[PATCH] checkout: add --fetch to fetch remote before resolving start-point

[PATCH] checkout: add --fetch to fetch remote before resolving start-point

[Harald Nordgren via GitGitGadget]

From: Harald Nordgren <haraldnordgren@gmail.com>

Add a --fetch option to git checkout and git switch, plus a
checkout.autoFetch config to enable it by default. When set and the
start-point argument names a configured remote (either bare, like
"origin", or prefixed, like "origin/foo"), fetch that remote before
resolving the ref. Aborts the checkout if the fetch fails.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
    checkout: add --fetch to fetch remote before resolving start-point
    
    A workflow I run several times a day looks like:
    
    git fetch origin
    git checkout -b new_branch origin/some-branch
    
    
    The first command exists purely to make the second one see an up-to-date
    view of the remote. If I forget it, origin/some-branch points at a stale
    commit, and I end up creating a local branch from the wrong starting
    point.
    
    This series teaches git checkout (and git switch) a new --fetch flag
    that folds the two steps into one:
    
    git checkout --fetch -b new_branch origin/some-branch
    
    
    When the start-point argument names a configured remote — either bare
    (origin, which resolves to the remote's default branch) or in / form —
    git fetch is run before the start-point is resolved. If the fetch fails,
    the checkout aborts and no local branch is created.
    
    A new checkout.autoFetch config option enables the same behavior by
    default, for users who always want it.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2281%2FHaraldNordgren%2Fcheckout-fetch-start-point-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2281/HaraldNordgren/checkout-fetch-start-point-v1
Pull-Request: https://github.com/git/git/pull/2281

 builtin/checkout.c    | 48 ++++++++++++++++++++++++++++++++++++++--
 t/t7201-co.sh         | 51 +++++++++++++++++++++++++++++++++++++++++++
 t/t9902-completion.sh |  1 +
 3 files changed, 98 insertions(+), 2 deletions(-)

diff --git a/builtin/checkout.c b/builtin/checkout.c
index e031e61886..c8fbc4923b 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -30,7 +30,9 @@
 #include "repo-settings.h"
 #include "resolve-undo.h"
 #include "revision.h"
+#include "run-command.h"
 #include "setup.h"
+#include "strvec.h"
 #include "submodule.h"
 #include "symlinks.h"
 #include "trace2.h"
@@ -61,6 +63,7 @@ struct checkout_opts {
 	int count_checkout_paths;
 	int overlay_mode;
 	int dwim_new_local_branch;
+	int auto_fetch;
 	int discard_changes;
 	int accept_ref;
 	int accept_pathspec;
@@ -112,6 +115,34 @@ struct branch_info {
 	char *checkout;
 };
 
+static void fetch_remote_for_start_point(const char *arg)
+{
+	const char *slash;
+	char *remote_name;
+	struct remote *remote;
+	struct child_process cmd = CHILD_PROCESS_INIT;
+
+	if (!arg || !*arg)
+		return;
+
+	slash = strchr(arg, '/');
+	if (slash == arg)
+		return;
+	remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
+
+	remote = remote_get(remote_name);
+	if (!remote || !remote_is_configured(remote, 1)) {
+		free(remote_name);
+		return;
+	}
+
+	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
+	cmd.git_cmd = 1;
+	free(remote_name);
+	if (run_command(&cmd))
+		die(_("failed to fetch start-point '%s'"), arg);
+}
+
 static void branch_info_release(struct branch_info *info)
 {
 	free(info->name);
@@ -1237,6 +1268,10 @@ static int git_checkout_config(const char *var, const char *value,
 		opts->dwim_new_local_branch = git_config_bool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "checkout.autofetch")) {
+		opts->auto_fetch = git_config_bool(var, value);
+		return 0;
+	}
 
 	if (starts_with(var, "submodule."))
 		return git_default_submodule_config(var, value, NULL);
@@ -1942,8 +1977,13 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 			opts->dwim_new_local_branch &&
 			opts->track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts->new_branch;
-		int n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
-					     &new_branch_info, opts, &rev);
+		int n;
+
+		if (opts->auto_fetch)
+			fetch_remote_for_start_point(argv[0]);
+
+		n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
+					 &new_branch_info, opts, &rev);
 		argv += n;
 		argc -= n;
 	} else if (!opts->accept_ref && opts->from_treeish) {
@@ -2052,6 +2092,8 @@ int cmd_checkout(int argc,
 		OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode (default)")),
 		OPT_BOOL(0, "auto-advance", &opts.auto_advance,
 			 N_("auto advance to the next file when selecting hunks interactively")),
+		OPT_BOOL(0, "fetch", &opts.auto_fetch,
+			 N_("fetch from the remote first if <start-point> is a remote-tracking ref")),
 		OPT_END()
 	};
 
@@ -2102,6 +2144,8 @@ int cmd_switch(int argc,
 			 N_("second guess 'git switch <no-such-branch>'")),
 		OPT_BOOL(0, "discard-changes", &opts.discard_changes,
 			 N_("throw away local modifications")),
+		OPT_BOOL(0, "fetch", &opts.auto_fetch,
+			 N_("fetch from the remote first if <start-point> is a remote-tracking ref")),
 		OPT_END()
 	};
 
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 9bcf7c0b40..60ddebd9c3 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -801,4 +801,55 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
 	test_cmp_config "" --default "" branch.main2.merge
 '
 
+test_expect_success 'setup upstream for --fetch tests' '
+	git checkout main &&
+	git init fetch_upstream &&
+	test_commit -C fetch_upstream u_main &&
+	git remote add fetch_upstream fetch_upstream &&
+	git fetch fetch_upstream &&
+	git -C fetch_upstream checkout -b fetch_new &&
+	test_commit -C fetch_upstream u_new
+'
+
+test_expect_success 'checkout --fetch -b picks up branch created upstream after clone' '
+	git checkout main &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
+	git checkout --fetch -b local_new fetch_upstream/fetch_new &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD
+'
+
+test_expect_success 'checkout --fetch with bare remote name fetches the remote' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_new2 &&
+	test_commit -C fetch_upstream u_new2 &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2 &&
+	git checkout --fetch -b local_from_remote fetch_upstream &&
+	git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2
+'
+
+test_expect_success 'checkout --fetch aborts and does not create branch on fetch failure' '
+	git checkout main &&
+	test_might_fail git branch -D bogus &&
+	test_must_fail git checkout --fetch -b bogus fetch_upstream/does_not_exist &&
+	test_must_fail git rev-parse --verify refs/heads/bogus
+'
+
+test_expect_success 'checkout.autoFetch=true enables fetching without --fetch' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_cfg &&
+	test_commit -C fetch_upstream u_cfg &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_cfg &&
+	git -c checkout.autoFetch=true checkout -b local_cfg fetch_upstream/fetch_cfg &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_cfg HEAD
+'
+
+test_expect_success 'switch --fetch -c picks up branch created upstream after clone' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_switch &&
+	test_commit -C fetch_upstream u_switch &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
+	git switch --fetch -c local_switch fetch_upstream/fetch_switch &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
+'
+
 test_done
diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
index 2f9a597ec7..dc1d63669f 100755
--- a/t/t9902-completion.sh
+++ b/t/t9902-completion.sh
@@ -2602,6 +2602,7 @@ test_expect_success 'double dash "git checkout"' '
 	--ignore-other-worktrees Z
 	--recurse-submodules Z
 	--auto-advance Z
+	--fetch Z
 	--progress Z
 	--guess Z
 	--no-guess Z

base-commit: 94f057755b7941b321fd11fec1b2e3ca5313a4e0
-- 
gitgitgadget

Re: [PATCH] checkout: add --fetch to fetch remote before resolving start-point

[Ramsay Jones]

On 24/04/2026 11:03 am, Harald Nordgren via GitGitGadget wrote:
> From: Harald Nordgren <haraldnordgren@gmail.com>
> 
> Add a --fetch option to git checkout and git switch, plus a
> checkout.autoFetch config to enable it by default. When set and the
> start-point argument names a configured remote (either bare, like
> "origin", or prefixed, like "origin/foo"), fetch that remote before
> resolving the ref. Aborts the checkout if the fetch fails.
> 
> Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
> ---

[snip]

>  
> diff --git a/t/t7201-co.sh b/t/t7201-co.sh
> index 9bcf7c0b40..60ddebd9c3 100755
> --- a/t/t7201-co.sh
> +++ b/t/t7201-co.sh
> @@ -801,4 +801,55 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
>  	test_cmp_config "" --default "" branch.main2.merge
>  '
>  
> +test_expect_success 'setup upstream for --fetch tests' '
> +	git checkout main &&
> +	git init fetch_upstream &&
> +	test_commit -C fetch_upstream u_main &&
> +	git remote add fetch_upstream fetch_upstream &&
> +	git fetch fetch_upstream &&
> +	git -C fetch_upstream checkout -b fetch_new &&
> +	test_commit -C fetch_upstream u_new
> +'
> +
> +test_expect_success 'checkout --fetch -b picks up branch created upstream after clone' '
> +	git checkout main &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
> +	git checkout --fetch -b local_new fetch_upstream/fetch_new &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD
> +'
> +
> +test_expect_success 'checkout --fetch with bare remote name fetches the remote' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_new2 &&
> +	test_commit -C fetch_upstream u_new2 &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2 &&
> +	git checkout --fetch -b local_from_remote fetch_upstream &&
> +	git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2
> +'
> +
> +test_expect_success 'checkout --fetch aborts and does not create branch on fetch failure' '
> +	git checkout main &&
> +	test_might_fail git branch -D bogus &&
> +	test_must_fail git checkout --fetch -b bogus fetch_upstream/does_not_exist &&
> +	test_must_fail git rev-parse --verify refs/heads/bogus
> +'
> +
> +test_expect_success 'checkout.autoFetch=true enables fetching without --fetch' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_cfg &&
> +	test_commit -C fetch_upstream u_cfg &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_cfg &&
> +	git -c checkout.autoFetch=true checkout -b local_cfg fetch_upstream/fetch_cfg &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_cfg HEAD
> +'
> +
> +test_expect_success 'switch --fetch -c picks up branch created upstream after clone' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_switch &&
> +	test_commit -C fetch_upstream u_switch &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
> +	git switch --fetch -c local_switch fetch_upstream/fetch_switch &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
> +'
> +

I was just skimming the list (so if this is not appropriate, please just ignore) and,
although I think '--no-fetch' will probably countermand the autoFetch config, I do not
see a test that confirms it.

Thanks.

ATB,
Ramsay Jones

Re: [PATCH] checkout: add --fetch to fetch remote before resolving start-point

[D. Ben Knoble]

On Fri, Apr 24, 2026 at 6:08 AM Harald Nordgren via GitGitGadget
<gitgitgadget@gmail.com> wrote:
>
> From: Harald Nordgren <haraldnordgren@gmail.com>
>
> Add a --fetch option to git checkout and git switch, plus a
> checkout.autoFetch config to enable it by default. When set and the
> start-point argument names a configured remote (either bare, like
> "origin", or prefixed, like "origin/foo"), fetch that remote before
> resolving the ref. Aborts the checkout if the fetch fails.
>
> Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
> ---
>     checkout: add --fetch to fetch remote before resolving start-point
>
>     A workflow I run several times a day looks like:
>
>     git fetch origin
>     git checkout -b new_branch origin/some-branch
>
>
>     The first command exists purely to make the second one see an up-to-date
>     view of the remote. If I forget it, origin/some-branch points at a stale
>     commit, and I end up creating a local branch from the wrong starting
>     point.

When you realize this, "git pull --rebase" should help correct it.

>
>     This series teaches git checkout (and git switch) a new --fetch flag
>     that folds the two steps into one:
>
>     git checkout --fetch -b new_branch origin/some-branch
>
>
>     When the start-point argument names a configured remote — either bare
>     (origin, which resolves to the remote's default branch) or in / form —
>     git fetch is run before the start-point is resolved. If the fetch fails,
>     the checkout aborts and no local branch is created.
>
>     A new checkout.autoFetch config option enables the same behavior by
>     default, for users who always want it.

I could certainly see this being convenient. (I don't have any comment
on the code at this time.)

Comments on Phillip's review

[Harald Nordgren]

> When you realize this, "git pull --rebase" should help correct it.

Sure. I always run with

```
git config --global pull.rebase=true
```

I love rebasing and recomdend it to all colleagues that will listen, but
it still sucks to expose yourself to a possible merge conflict when you
realize you worked hours on top of a stale main branch.

> I could certainly see this being convenient.

🙌🏻


Harald

Wrong subject line

[Harald Nordgren]

I know you are not Ben. Forgot to change the subject line from a previous message.


Harald

Re: [PATCH] checkout: add --fetch to fetch remote before resolving start-point

[Kristoffer Haugsbakk]

On Fri, Apr 24, 2026, at 12:03, Harald Nordgren via GitGitGadget wrote:
> From: Harald Nordgren <haraldnordgren@gmail.com>
>
> Add a --fetch option to git checkout and git switch, plus a
> checkout.autoFetch config to enable it by default. When set and the

Why is the config not `checkout.config`? So it’s named the same as the
option (modulo snake case/camel case which is not relevant here).

> start-point argument names a configured remote (either bare, like
> "origin", or prefixed, like "origin/foo"),

It’s great that it only fetches when you have a remote-tracking branch
or alias for `<remote>/HEAD`. Doing a fetch on every <start-point> would
have been bad.

> fetch that remote before
> resolving the ref. Aborts the checkout if the fetch fails.
>
> Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
> ---
>     checkout: add --fetch to fetch remote before resolving start-point
>
>     A workflow I run several times a day looks like:
>
>     git fetch origin
>     git checkout -b new_branch origin/some-branch
>
>
>     The first command exists purely to make the second one see an up-to-date
>     view of the remote. If I forget it, origin/some-branch points at a stale
>     commit, and I end up creating a local branch from the wrong starting
>     point.
>
>     This series teaches git checkout (and git switch) a new --fetch flag
>     that folds the two steps into one:
>
>     git checkout --fetch -b new_branch origin/some-branch

The motivation for why this is being proposed maybe might as well go in
the commit message. Maybe that’s just me.

The commit message just says that “this thing is added”. Not why.

>
>
>     When the start-point argument names a configured remote — either bare
>     (origin, which resolves to the remote's default branch) or in / form —
>     git fetch is run before the start-point is resolved. If the fetch fails,
>     the checkout aborts and no local branch is created.
>
>     A new checkout.autoFetch config option enables the same behavior by
>     default, for users who always want it.
>
> Published-As:
> https://github.com/gitgitgadget/git/releases/tag/pr-git-2281%2FHaraldNordgren%2Fcheckout-fetch-start-point-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git
> pr-git-2281/HaraldNordgren/checkout-fetch-start-point-v1
> Pull-Request: https://github.com/git/git/pull/2281
>
>  builtin/checkout.c    | 48 ++++++++++++++++++++++++++++++++++++++--
>  t/t7201-co.sh         | 51 +++++++++++++++++++++++++++++++++++++++++++
>  t/t9902-completion.sh |  1 +
>  3 files changed, 98 insertions(+), 2 deletions(-)

I guess a later version will have the changes to the documentation.

>
> diff --git a/builtin/checkout.c b/builtin/checkout.c
>[snip]
>  		argv += n;
>  		argc -= n;
>  	} else if (!opts->accept_ref && opts->from_treeish) {
> @@ -2052,6 +2092,8 @@ int cmd_checkout(int argc,
>  		OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode
> (default)")),
>  		OPT_BOOL(0, "auto-advance", &opts.auto_advance,
>  			 N_("auto advance to the next file when selecting hunks
> interactively")),
> +		OPT_BOOL(0, "fetch", &opts.auto_fetch,
> +			 N_("fetch from the remote first if <start-point> is a remote-tracking ref")),

s/remote-tracking ref/remote-tracking branch/ ?

git(1) doesn’t have a namespace for tracking refs in general.

>  		OPT_END()
>  	};
>
> @@ -2102,6 +2144,8 @@ int cmd_switch(int argc,
>  			 N_("second guess 'git switch <no-such-branch>'")),
>  		OPT_BOOL(0, "discard-changes", &opts.discard_changes,
>  			 N_("throw away local modifications")),
> +		OPT_BOOL(0, "fetch", &opts.auto_fetch,
> +			 N_("fetch from the remote first if <start-point> is a remote-tracking ref")),

Ditto.

>  		OPT_END()
>  	};
>[snip]

Comments on Phillip's review

[Harald Nordgren]

> > Add a --fetch option to git checkout and git switch, plus a
> > checkout.autoFetch config to enable it by default. When set and the
> 
> Why is the config not `checkout.config`? So it’s named the same as the
> option (modulo snake case/camel case which is not relevant here).

Will rename the config to 'checkout.fetch'.

> The motivation for why this is being proposed maybe might as well go in
> the commit message. Maybe that’s just me.
> 
> The commit message just says that “this thing is added”. Not why.

I will update it.

> I guess a later version will have the changes to the documentation.

I forgot that, will add it!

> s/remote-tracking ref/remote-tracking branch/ ?
> 
> git(1) doesn’t have a namespace for tracking refs in general.

👍


Harald

Wrong subject line

[Harald Nordgren]

I know you are not Ben. Forgot to change the subject line from a previous message.


Harald

Re: Wrong subject line

[Kristoffer Haugsbakk]

On Sat, Apr 25, 2026, at 19:44, Harald Nordgren wrote:
> I know you are not Ben. Forgot to change the subject line from a
> previous message.

You mean I’m not Phillip. ;)

    Subject: Comments on Phillip's review

I don’t understand why you change the email subjects so often. Right now
I had three “Wrong subject line” in my inbox with lost threading
(webmail client) with the only way to distinguish them being that I was
the the CC on this one.

Most of the time whole 100-email threads like patch series never change
the subject. And to me it is easier to keep track of those “RE: [PATCH
v5] florb: drop glorb” than if someone changes the subject to e.g.
“Regarding memory leaks” because someone found a memory leak in a
review. Because that was a reply to an email from two days ago, but I’ve
been a away for a week so I think it’s a new thread about
something else.

That’s just my experience. My amateur webmail setup doesn’t really
matter here since I just dip in/interrupt threads when I feel like it.

Re: [PATCH] remote: add --set-head option to 'git remote add'

[Harald Nordgren]

> I don’t understand why you change the email subjects so often. Right now
> I had three “Wrong subject line” in my inbox with lost threading
> (webmail client) with the only way to distinguish them being that I was
> the the CC on this one.
> 
> Most of the time whole 100-email threads like patch series never change
> the subject. And to me it is easier to keep track of those “RE: [PATCH
> v5] florb: drop glorb” than if someone changes the subject to e.g.
> “Regarding memory leaks” because someone found a memory leak in a
> review. Because that was a reply to an email from two days ago, but I’ve
> been a away for a week so I think it’s a new thread about
> something else.

I got some feedback before, not from you, that subject lines should be
more varied, probably there is a golden middle that I need to find.

And I fundamentally agree with you.


Harald

Re: [PATCH] checkout: add --fetch to fetch remote before resolving start-point

[Marc Branchaud]

On 2026-04-24 04:03, Harald Nordgren via GitGitGadget wrote:
> From: Harald Nordgren <haraldnordgren@gmail.com>
> 
> Add a --fetch option to git checkout and git switch, plus a
> checkout.autoFetch config to enable it by default. When set and the
> start-point argument names a configured remote (either bare, like
> "origin", or prefixed, like "origin/foo"), fetch that remote before
> resolving the ref. Aborts the checkout if the fetch fails.

Why tie the behaviour to the nature of the start-point?  That seems 
over-designed and prone to tripping people up.  Are you trying to cater 
to users who have multiple remotes?

I can imagine people who just want to do a checkout of anything after 
fetching -- maybe they want to checkout a new tag, or some other 
detached HEAD, or just an already-existing local branch.  They see that 
checkout has this nifty --fetch option so they think they can combine
	git fetch; git checkout
into a single command ... but no, only if they checkout something in a 
remote's namespace.

I don't personally feel the need for this new option, but I think you'll 
have a much easier time implementing and maintaining it if you just make 
--fetch do a plain fetch without caring about what the starting-point is.

		M.


> Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
> ---
>      checkout: add --fetch to fetch remote before resolving start-point
>      
>      A workflow I run several times a day looks like:
>      
>      git fetch origin
>      git checkout -b new_branch origin/some-branch
>      
>      
>      The first command exists purely to make the second one see an up-to-date
>      view of the remote. If I forget it, origin/some-branch points at a stale
>      commit, and I end up creating a local branch from the wrong starting
>      point.
>      
>      This series teaches git checkout (and git switch) a new --fetch flag
>      that folds the two steps into one:
>      
>      git checkout --fetch -b new_branch origin/some-branch
>      
>      
>      When the start-point argument names a configured remote — either bare
>      (origin, which resolves to the remote's default branch) or in / form —
>      git fetch is run before the start-point is resolved. If the fetch fails,
>      the checkout aborts and no local branch is created.
>      
>      A new checkout.autoFetch config option enables the same behavior by
>      default, for users who always want it.
> 
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2281%2FHaraldNordgren%2Fcheckout-fetch-start-point-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2281/HaraldNordgren/checkout-fetch-start-point-v1
> Pull-Request: https://github.com/git/git/pull/2281
> 
>   builtin/checkout.c    | 48 ++++++++++++++++++++++++++++++++++++++--
>   t/t7201-co.sh         | 51 +++++++++++++++++++++++++++++++++++++++++++
>   t/t9902-completion.sh |  1 +
>   3 files changed, 98 insertions(+), 2 deletions(-)
> 
> diff --git a/builtin/checkout.c b/builtin/checkout.c
> index e031e61886..c8fbc4923b 100644
> --- a/builtin/checkout.c
> +++ b/builtin/checkout.c
> @@ -30,7 +30,9 @@
>   #include "repo-settings.h"
>   #include "resolve-undo.h"
>   #include "revision.h"
> +#include "run-command.h"
>   #include "setup.h"
> +#include "strvec.h"
>   #include "submodule.h"
>   #include "symlinks.h"
>   #include "trace2.h"
> @@ -61,6 +63,7 @@ struct checkout_opts {
>   	int count_checkout_paths;
>   	int overlay_mode;
>   	int dwim_new_local_branch;
> +	int auto_fetch;
>   	int discard_changes;
>   	int accept_ref;
>   	int accept_pathspec;
> @@ -112,6 +115,34 @@ struct branch_info {
>   	char *checkout;
>   };
>   
> +static void fetch_remote_for_start_point(const char *arg)
> +{
> +	const char *slash;
> +	char *remote_name;
> +	struct remote *remote;
> +	struct child_process cmd = CHILD_PROCESS_INIT;
> +
> +	if (!arg || !*arg)
> +		return;
> +
> +	slash = strchr(arg, '/');
> +	if (slash == arg)
> +		return;
> +	remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
> +
> +	remote = remote_get(remote_name);
> +	if (!remote || !remote_is_configured(remote, 1)) {
> +		free(remote_name);
> +		return;
> +	}
> +
> +	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
> +	cmd.git_cmd = 1;
> +	free(remote_name);
> +	if (run_command(&cmd))
> +		die(_("failed to fetch start-point '%s'"), arg);
> +}
> +
>   static void branch_info_release(struct branch_info *info)
>   {
>   	free(info->name);
> @@ -1237,6 +1268,10 @@ static int git_checkout_config(const char *var, const char *value,
>   		opts->dwim_new_local_branch = git_config_bool(var, value);
>   		return 0;
>   	}
> +	if (!strcmp(var, "checkout.autofetch")) {
> +		opts->auto_fetch = git_config_bool(var, value);
> +		return 0;
> +	}
>   
>   	if (starts_with(var, "submodule."))
>   		return git_default_submodule_config(var, value, NULL);
> @@ -1942,8 +1977,13 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
>   			opts->dwim_new_local_branch &&
>   			opts->track == BRANCH_TRACK_UNSPECIFIED &&
>   			!opts->new_branch;
> -		int n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
> -					     &new_branch_info, opts, &rev);
> +		int n;
> +
> +		if (opts->auto_fetch)
> +			fetch_remote_for_start_point(argv[0]);
> +
> +		n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
> +					 &new_branch_info, opts, &rev);
>   		argv += n;
>   		argc -= n;
>   	} else if (!opts->accept_ref && opts->from_treeish) {
> @@ -2052,6 +2092,8 @@ int cmd_checkout(int argc,
>   		OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode (default)")),
>   		OPT_BOOL(0, "auto-advance", &opts.auto_advance,
>   			 N_("auto advance to the next file when selecting hunks interactively")),
> +		OPT_BOOL(0, "fetch", &opts.auto_fetch,
> +			 N_("fetch from the remote first if <start-point> is a remote-tracking ref")),
>   		OPT_END()
>   	};
>   
> @@ -2102,6 +2144,8 @@ int cmd_switch(int argc,
>   			 N_("second guess 'git switch <no-such-branch>'")),
>   		OPT_BOOL(0, "discard-changes", &opts.discard_changes,
>   			 N_("throw away local modifications")),
> +		OPT_BOOL(0, "fetch", &opts.auto_fetch,
> +			 N_("fetch from the remote first if <start-point> is a remote-tracking ref")),
>   		OPT_END()
>   	};
>   
> diff --git a/t/t7201-co.sh b/t/t7201-co.sh
> index 9bcf7c0b40..60ddebd9c3 100755
> --- a/t/t7201-co.sh
> +++ b/t/t7201-co.sh
> @@ -801,4 +801,55 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
>   	test_cmp_config "" --default "" branch.main2.merge
>   '
>   
> +test_expect_success 'setup upstream for --fetch tests' '
> +	git checkout main &&
> +	git init fetch_upstream &&
> +	test_commit -C fetch_upstream u_main &&
> +	git remote add fetch_upstream fetch_upstream &&
> +	git fetch fetch_upstream &&
> +	git -C fetch_upstream checkout -b fetch_new &&
> +	test_commit -C fetch_upstream u_new
> +'
> +
> +test_expect_success 'checkout --fetch -b picks up branch created upstream after clone' '
> +	git checkout main &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
> +	git checkout --fetch -b local_new fetch_upstream/fetch_new &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD
> +'
> +
> +test_expect_success 'checkout --fetch with bare remote name fetches the remote' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_new2 &&
> +	test_commit -C fetch_upstream u_new2 &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2 &&
> +	git checkout --fetch -b local_from_remote fetch_upstream &&
> +	git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2
> +'
> +
> +test_expect_success 'checkout --fetch aborts and does not create branch on fetch failure' '
> +	git checkout main &&
> +	test_might_fail git branch -D bogus &&
> +	test_must_fail git checkout --fetch -b bogus fetch_upstream/does_not_exist &&
> +	test_must_fail git rev-parse --verify refs/heads/bogus
> +'
> +
> +test_expect_success 'checkout.autoFetch=true enables fetching without --fetch' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_cfg &&
> +	test_commit -C fetch_upstream u_cfg &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_cfg &&
> +	git -c checkout.autoFetch=true checkout -b local_cfg fetch_upstream/fetch_cfg &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_cfg HEAD
> +'
> +
> +test_expect_success 'switch --fetch -c picks up branch created upstream after clone' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_switch &&
> +	test_commit -C fetch_upstream u_switch &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
> +	git switch --fetch -c local_switch fetch_upstream/fetch_switch &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
> +'
> +
>   test_done
> diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
> index 2f9a597ec7..dc1d63669f 100755
> --- a/t/t9902-completion.sh
> +++ b/t/t9902-completion.sh
> @@ -2602,6 +2602,7 @@ test_expect_success 'double dash "git checkout"' '
>   	--ignore-other-worktrees Z
>   	--recurse-submodules Z
>   	--auto-advance Z
> +	--fetch Z
>   	--progress Z
>   	--guess Z
>   	--no-guess Z
> 
> base-commit: 94f057755b7941b321fd11fec1b2e3ca5313a4e0

Wrong subject line

[Harald Nordgren]

I know you are not Ben. Forgot to change the subject line from a previous message.


Harald

Re: [PATCH] checkout: add --fetch to fetch remote before resolving start-point

[Junio C Hamano]

"Harald Nordgren via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Harald Nordgren <haraldnordgren@gmail.com>
>
> Add a --fetch option to git checkout and git switch, plus a
> checkout.autoFetch config to enable it by default. When set and the
> start-point argument names a configured remote (either bare, like
> "origin", or prefixed, like "origin/foo"), fetch that remote before
> resolving the ref. Aborts the checkout if the fetch fails.
>
> Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
> ---

It is true that "checkout" does funny things to special case the
remote-tracking branches, like setting up the branch.<name>.merge
configuration or even inferring the name of the local branch to be
created.  

But I have to say that this one, especially the configuration
variable, goes way too far.  The usual uses of remote-tracking
branch names, e.g.,

    git log -1 origin/master
    git grep frotz origin/master
    git rev-list --count origin/maint..origin/master

to name a specific object all assume and rely on the stability of
them.  Should the configuration cause a fetch to happen before any
of these uses of remote-tracking branches for consistency?

Re: [PATCH] checkout: add --fetch to fetch remote before resolving start-point

[Junio C Hamano]

Junio C Hamano <gitster@pobox.com> writes:

> "Harald Nordgren via GitGitGadget" <gitgitgadget@gmail.com> writes:
>
>> From: Harald Nordgren <haraldnordgren@gmail.com>
>>
>> Add a --fetch option to git checkout and git switch, plus a
>> checkout.autoFetch config to enable it by default. When set and the
>> start-point argument names a configured remote (either bare, like
>> "origin", or prefixed, like "origin/foo"), fetch that remote before
>> resolving the ref. Aborts the checkout if the fetch fails.
>>
>> Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
>> ---
>
> It is true that "checkout" does funny things to special case the
> remote-tracking branches, like setting up the branch.<name>.merge
> configuration or even inferring the name of the local branch to be
> created.  
> ...
> ...  Should the configuration cause a fetch to happen before any
> of these uses of remote-tracking branches for consistency?

The last one was a rhetorical question.  I do not want to see such a
configuration variable to implicitly trigger fetching at all.

I am somewhat sympathetic to the desire "I want to be sure that I
start the new branch in a state as fresh as possible".  It is tied
to the "--track" option of "git checkout -b topic --track
origin/main".  If you are merely starting at a single arbitrary
commit, instead of anticipating to having to repeatedly sync with
the remote-tracking branch that will subsequently move, there is no
point jumping to a "freshest" commit that you haven't even seen let
alone inspected (i.e., you do not even know if it is a good base to
build on).

So instead of introducing a totally new option that can only be used
only when "--track" is given, it might make more sense to introduce
this as a variant of "--track", perhaps "--track=fetch,[in]direct"
or something like that.  And extend branch.autosetup{Merge,Rebase}
that controls what happens when a branch is created with "checkout
-t -b" or "branch --track" so that the remote-tracking branch gets
updated, perhaps.

As to "git checkout origin/main" (nothing else on the command line),
it has "magic" compared to "git checkout origin/main~0" already by
treating the parameter not just as a SHA-1 expression that names a
commit object but as a remote-tracking branch (this is necessary for
"-t").  So I am not fundamentally opposed to the idea to give an
option to treat that form specifically.

Having said all that, quite honestly, I prefer not to see any of the
above changes, including the original patch.  It leaves too many
usability questions unaddressed.  For a starter, if you interact
with a repository with two or more branches, should

   $ git checkout --track=fetch -b topic origin/main

update an unrelated remote-tracking branch origin/maint from the
same remote?  As I already said, most Git tools _depend_ on the
stability of remote-tracking branches---the desire to update the
origin/main when a new branch that builds on origin/main is created
may be a valid one, but it is unclear if that warrants updating
other remote-tracking branches only because they come from the same
remote repository.  There may be a dozen other UI/usability issues
that will be introduced if we start to "fetch from remote"
automatically, but I won't even try to be exhaustive while I am
still on a leave ;-)

Multiple remotes

[Harald Nordgren]

> The last one was a rhetorical question.  I do not want to see such a
> configuration variable to implicitly trigger fetching at all.

🤣

Good to clarify that when working with me so that I don't go ahead and
implement that!

> If you are merely starting at a single arbitrary
> commit, instead of anticipating to having to repeatedly sync with
> the remote-tracking branch that will subsequently move, there is no
> point jumping to a "freshest" commit that you haven't even seen let
> alone inspected (i.e., you do not even know if it is a good base to
> build on).

Not sure I understand this sentiment. For better or worse, the latest
commit will decide what you have to work with -- unless we expect it to be
reverted or forced pushed over.

What better starting point is there?

> For a starter, if you interact
> with a repository with two or more branches, should
> 
>    $ git checkout --track=fetch -b topic origin/main
> 
> update an unrelated remote-tracking branch origin/maint from the
> same remote?  As I already said, most Git tools _depend_ on the
> stability of remote-tracking branches

This is an interesting question, and it's very likely that I am missing
some nuance here. However, with that said what option does the developer
have, you have to accept that the upstream changes constantly when others
are working on it. What good does it do to keep the "head in the sand" any
longer than necessary?

I'm not sure there is a way to fetch only 'origin/main' and avoid
'origin/maint'? Maybe, maybe, if that exists it could be useful here.

> still on a leave

Enjoy your vacation! I don't expect any response from you until you're back!


Harald

Re: Multiple remotes

[Ben Knoble]

> Le 25 avr. 2026 à 13:58, Harald Nordgren <haraldnordgren@gmail.com> a écrit :
> 
> 
>> 
>> The last one was a rhetorical question.  I do not want to see such a
>> configuration variable to implicitly trigger fetching at all.
> 
> 🤣
> 
> Good to clarify that when working with me so that I don't go ahead and
> implement that!
> 
>> If you are merely starting at a single arbitrary
>> commit, instead of anticipating to having to repeatedly sync with
>> the remote-tracking branch that will subsequently move, there is no
>> point jumping to a "freshest" commit that you haven't even seen let
>> alone inspected (i.e., you do not even know if it is a good base to
>> build on).
> 
> Not sure I understand this sentiment. For better or worse, the latest
> commit will decide what you have to work with -- unless we expect it to be
> reverted or forced pushed over.
> 
> What better starting point is there?
> 
>> For a starter, if you interact
>> with a repository with two or more branches, should
>> 
>>   $ git checkout --track=fetch -b topic origin/main
>> 
>> update an unrelated remote-tracking branch origin/maint from the
>> same remote?  As I already said, most Git tools _depend_ on the
>> stability of remote-tracking branches
> 
> This is an interesting question, and it's very likely that I am missing
> some nuance here. However, with that said what option does the developer
> have, you have to accept that the upstream changes constantly when others
> are working on it. What good does it do to keep the "head in the sand" any
> longer than necessary?
> 
> I'm not sure there is a way to fetch only 'origin/main' and avoid
> 'origin/maint'? Maybe, maybe, if that exists it could be useful here.

Isn’t that exactly what

    git fetch origin main

does? (Might need to expand the refspec.)

> 
>> still on a leave
> 
> Enjoy your vacation! I don't expect any response from you until you're back!
> 
> 
> Harald
> 

gh

[Harald Nordgren]

> Isn’t that exactly what
> 
>     git fetch origin main
> 
> does? (Might need to expand the refspec.)

Very good point, I will update it!


Harald

[PATCH v2] checkout: add --fetch to fetch remote before resolving start-point

[Harald Nordgren via GitGitGadget]

From: Harald Nordgren <haraldnordgren@gmail.com>

A common workflow is:

    git fetch origin
    git checkout -b new_branch origin/some-branch

The first command exists purely so the second sees an up-to-date view
of the remote. If it is forgotten, origin/some-branch points at a stale
commit and the new local branch is created from the wrong start point.

Teach checkout (and switch) a --fetch flag that folds the two steps
into one:

    git checkout --fetch -b new_branch origin/some-branch

When --fetch is given and <start-point> names a configured remote
(either bare, like "origin", or prefixed, like "origin/foo"), fetch
that remote before resolving the ref. Abort the checkout if the fetch
fails.

Also add a checkout.fetch config to enable this by default.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
    checkout: add --fetch to fetch remote before resolving start-point
    
     * Rename the config from checkout.autoFetch to checkout.fetch, so it
       matches the --fetch option name.
    
     * Rename the internal struct field from auto_fetch to fetch for
       consistency with the option and config names.
    
     * Reword the commit message to lead with the problem (forgetting 'git
       fetch' and ending up with a stale start-point) before describing the
       solution.
    
     * Document --fetch / --no-fetch in git-checkout and git-switch, and
       document checkout.fetch in the config reference.
    
     * Use "remote-tracking branch" instead of "remote-tracking ref" in the
       option help text.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2281%2FHaraldNordgren%2Fcheckout-fetch-start-point-v2
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2281/HaraldNordgren/checkout-fetch-start-point-v2
Pull-Request: https://github.com/git/git/pull/2281

Range-diff vs v1:

 1:  e2fa50ff40 ! 1:  13074c9fea checkout: add --fetch to fetch remote before resolving start-point
     @@ Metadata
       ## Commit message ##
          checkout: add --fetch to fetch remote before resolving start-point
      
     -    Add a --fetch option to git checkout and git switch, plus a
     -    checkout.autoFetch config to enable it by default. When set and the
     -    start-point argument names a configured remote (either bare, like
     -    "origin", or prefixed, like "origin/foo"), fetch that remote before
     -    resolving the ref. Aborts the checkout if the fetch fails.
     +    A common workflow is:
     +
     +        git fetch origin
     +        git checkout -b new_branch origin/some-branch
     +
     +    The first command exists purely so the second sees an up-to-date view
     +    of the remote. If it is forgotten, origin/some-branch points at a stale
     +    commit and the new local branch is created from the wrong start point.
     +
     +    Teach checkout (and switch) a --fetch flag that folds the two steps
     +    into one:
     +
     +        git checkout --fetch -b new_branch origin/some-branch
     +
     +    When --fetch is given and <start-point> names a configured remote
     +    (either bare, like "origin", or prefixed, like "origin/foo"), fetch
     +    that remote before resolving the ref. Abort the checkout if the fetch
     +    fails.
     +
     +    Also add a checkout.fetch config to enable this by default.
      
          Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
      
     + ## Documentation/config/checkout.adoc ##
     +@@ Documentation/config/checkout.adoc: commands or functionality in the future.
     + 	option in `git checkout` and `git switch`. See
     + 	linkgit:git-switch[1] and linkgit:git-checkout[1].
     + 
     ++`checkout.fetch`::
     ++	Provides the default value for the `--fetch` or `--no-fetch`
     ++	option in `git checkout` and `git switch`. See
     ++	linkgit:git-switch[1] and linkgit:git-checkout[1].
     ++
     + `checkout.workers`::
     + 	The number of parallel workers to use when updating the working tree.
     + 	The default is one, i.e. sequential execution. If set to a value less
     +
     + ## Documentation/git-checkout.adoc ##
     +@@ Documentation/git-checkout.adoc: linkgit:git-config[1].
     + The default behavior can be set via the `checkout.guess` configuration
     + variable.
     + 
     ++`--fetch`::
     ++`--no-fetch`::
     ++	If _<start-point>_ names a configured remote -- either bare,
     ++	like `origin` (which resolves to the remote's default branch),
     ++	or in _<remote>/<branch>_ form -- run `git fetch` on that
     ++	remote before resolving _<start-point>_. If the fetch fails,
     ++	the checkout is aborted and no local branch is created.
     +++
     ++The default behavior can be set via the `checkout.fetch` configuration
     ++variable.
     ++
     + `-l`::
     + 	Create the new branch's reflog; see linkgit:git-branch[1] for
     + 	details.
     +
     + ## Documentation/git-switch.adoc ##
     +@@ Documentation/git-switch.adoc: ambiguous but exists on the 'origin' remote. See also
     + The default behavior can be set via the `checkout.guess` configuration
     + variable.
     + 
     ++`--fetch`::
     ++`--no-fetch`::
     ++	If _<start-point>_ names a configured remote -- either bare,
     ++	like `origin` (which resolves to the remote's default branch),
     ++	or in _<remote>/<branch>_ form -- run `git fetch` on that
     ++	remote before resolving _<start-point>_. If the fetch fails,
     ++	the switch is aborted and no local branch is created.
     +++
     ++The default behavior can be set via the `checkout.fetch` configuration
     ++variable.
     ++
     + `-f`::
     + `--force`::
     + 	An alias for `--discard-changes`.
     +
       ## builtin/checkout.c ##
      @@
       #include "repo-settings.h"
     @@ builtin/checkout.c: struct checkout_opts {
       	int count_checkout_paths;
       	int overlay_mode;
       	int dwim_new_local_branch;
     -+	int auto_fetch;
     ++	int fetch;
       	int discard_changes;
       	int accept_ref;
       	int accept_pathspec;
     @@ builtin/checkout.c: static int git_checkout_config(const char *var, const char *
       		opts->dwim_new_local_branch = git_config_bool(var, value);
       		return 0;
       	}
     -+	if (!strcmp(var, "checkout.autofetch")) {
     -+		opts->auto_fetch = git_config_bool(var, value);
     ++	if (!strcmp(var, "checkout.fetch")) {
     ++		opts->fetch = git_config_bool(var, value);
      +		return 0;
      +	}
       
     @@ builtin/checkout.c: static int checkout_main(int argc, const char **argv, const
      -					     &new_branch_info, opts, &rev);
      +		int n;
      +
     -+		if (opts->auto_fetch)
     ++		if (opts->fetch)
      +			fetch_remote_for_start_point(argv[0]);
      +
      +		n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
     @@ builtin/checkout.c: int cmd_checkout(int argc,
       		OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode (default)")),
       		OPT_BOOL(0, "auto-advance", &opts.auto_advance,
       			 N_("auto advance to the next file when selecting hunks interactively")),
     -+		OPT_BOOL(0, "fetch", &opts.auto_fetch,
     -+			 N_("fetch from the remote first if <start-point> is a remote-tracking ref")),
     ++		OPT_BOOL(0, "fetch", &opts.fetch,
     ++			 N_("fetch from the remote first if <start-point> is a remote-tracking branch")),
       		OPT_END()
       	};
       
     @@ builtin/checkout.c: int cmd_switch(int argc,
       			 N_("second guess 'git switch <no-such-branch>'")),
       		OPT_BOOL(0, "discard-changes", &opts.discard_changes,
       			 N_("throw away local modifications")),
     -+		OPT_BOOL(0, "fetch", &opts.auto_fetch,
     -+			 N_("fetch from the remote first if <start-point> is a remote-tracking ref")),
     ++		OPT_BOOL(0, "fetch", &opts.fetch,
     ++			 N_("fetch from the remote first if <start-point> is a remote-tracking branch")),
       		OPT_END()
       	};
       
     @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh
      +	test_must_fail git rev-parse --verify refs/heads/bogus
      +'
      +
     -+test_expect_success 'checkout.autoFetch=true enables fetching without --fetch' '
     ++test_expect_success 'checkout.fetch=true enables fetching without --fetch' '
      +	git checkout main &&
      +	git -C fetch_upstream checkout -b fetch_cfg &&
      +	test_commit -C fetch_upstream u_cfg &&
      +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_cfg &&
     -+	git -c checkout.autoFetch=true checkout -b local_cfg fetch_upstream/fetch_cfg &&
     ++	git -c checkout.fetch=true checkout -b local_cfg fetch_upstream/fetch_cfg &&
      +	test_cmp_rev refs/remotes/fetch_upstream/fetch_cfg HEAD
      +'
      +


 Documentation/config/checkout.adoc |  5 +++
 Documentation/git-checkout.adoc    | 11 +++++++
 Documentation/git-switch.adoc      | 11 +++++++
 builtin/checkout.c                 | 48 ++++++++++++++++++++++++++--
 t/t7201-co.sh                      | 51 ++++++++++++++++++++++++++++++
 t/t9902-completion.sh              |  1 +
 6 files changed, 125 insertions(+), 2 deletions(-)

diff --git a/Documentation/config/checkout.adoc b/Documentation/config/checkout.adoc
index e35d212969..c95f72b38e 100644
--- a/Documentation/config/checkout.adoc
+++ b/Documentation/config/checkout.adoc
@@ -22,6 +22,11 @@ commands or functionality in the future.
 	option in `git checkout` and `git switch`. See
 	linkgit:git-switch[1] and linkgit:git-checkout[1].
 
+`checkout.fetch`::
+	Provides the default value for the `--fetch` or `--no-fetch`
+	option in `git checkout` and `git switch`. See
+	linkgit:git-switch[1] and linkgit:git-checkout[1].
+
 `checkout.workers`::
 	The number of parallel workers to use when updating the working tree.
 	The default is one, i.e. sequential execution. If set to a value less
diff --git a/Documentation/git-checkout.adoc b/Documentation/git-checkout.adoc
index 43ccf47cf6..f20e2f4c8c 100644
--- a/Documentation/git-checkout.adoc
+++ b/Documentation/git-checkout.adoc
@@ -201,6 +201,17 @@ linkgit:git-config[1].
 The default behavior can be set via the `checkout.guess` configuration
 variable.
 
+`--fetch`::
+`--no-fetch`::
+	If _<start-point>_ names a configured remote -- either bare,
+	like `origin` (which resolves to the remote's default branch),
+	or in _<remote>/<branch>_ form -- run `git fetch` on that
+	remote before resolving _<start-point>_. If the fetch fails,
+	the checkout is aborted and no local branch is created.
++
+The default behavior can be set via the `checkout.fetch` configuration
+variable.
+
 `-l`::
 	Create the new branch's reflog; see linkgit:git-branch[1] for
 	details.
diff --git a/Documentation/git-switch.adoc b/Documentation/git-switch.adoc
index 87707e9265..3826ed9066 100644
--- a/Documentation/git-switch.adoc
+++ b/Documentation/git-switch.adoc
@@ -110,6 +110,17 @@ ambiguous but exists on the 'origin' remote. See also
 The default behavior can be set via the `checkout.guess` configuration
 variable.
 
+`--fetch`::
+`--no-fetch`::
+	If _<start-point>_ names a configured remote -- either bare,
+	like `origin` (which resolves to the remote's default branch),
+	or in _<remote>/<branch>_ form -- run `git fetch` on that
+	remote before resolving _<start-point>_. If the fetch fails,
+	the switch is aborted and no local branch is created.
++
+The default behavior can be set via the `checkout.fetch` configuration
+variable.
+
 `-f`::
 `--force`::
 	An alias for `--discard-changes`.
diff --git a/builtin/checkout.c b/builtin/checkout.c
index e031e61886..b2a34f0f00 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -30,7 +30,9 @@
 #include "repo-settings.h"
 #include "resolve-undo.h"
 #include "revision.h"
+#include "run-command.h"
 #include "setup.h"
+#include "strvec.h"
 #include "submodule.h"
 #include "symlinks.h"
 #include "trace2.h"
@@ -61,6 +63,7 @@ struct checkout_opts {
 	int count_checkout_paths;
 	int overlay_mode;
 	int dwim_new_local_branch;
+	int fetch;
 	int discard_changes;
 	int accept_ref;
 	int accept_pathspec;
@@ -112,6 +115,34 @@ struct branch_info {
 	char *checkout;
 };
 
+static void fetch_remote_for_start_point(const char *arg)
+{
+	const char *slash;
+	char *remote_name;
+	struct remote *remote;
+	struct child_process cmd = CHILD_PROCESS_INIT;
+
+	if (!arg || !*arg)
+		return;
+
+	slash = strchr(arg, '/');
+	if (slash == arg)
+		return;
+	remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
+
+	remote = remote_get(remote_name);
+	if (!remote || !remote_is_configured(remote, 1)) {
+		free(remote_name);
+		return;
+	}
+
+	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
+	cmd.git_cmd = 1;
+	free(remote_name);
+	if (run_command(&cmd))
+		die(_("failed to fetch start-point '%s'"), arg);
+}
+
 static void branch_info_release(struct branch_info *info)
 {
 	free(info->name);
@@ -1237,6 +1268,10 @@ static int git_checkout_config(const char *var, const char *value,
 		opts->dwim_new_local_branch = git_config_bool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "checkout.fetch")) {
+		opts->fetch = git_config_bool(var, value);
+		return 0;
+	}
 
 	if (starts_with(var, "submodule."))
 		return git_default_submodule_config(var, value, NULL);
@@ -1942,8 +1977,13 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 			opts->dwim_new_local_branch &&
 			opts->track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts->new_branch;
-		int n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
-					     &new_branch_info, opts, &rev);
+		int n;
+
+		if (opts->fetch)
+			fetch_remote_for_start_point(argv[0]);
+
+		n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
+					 &new_branch_info, opts, &rev);
 		argv += n;
 		argc -= n;
 	} else if (!opts->accept_ref && opts->from_treeish) {
@@ -2052,6 +2092,8 @@ int cmd_checkout(int argc,
 		OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode (default)")),
 		OPT_BOOL(0, "auto-advance", &opts.auto_advance,
 			 N_("auto advance to the next file when selecting hunks interactively")),
+		OPT_BOOL(0, "fetch", &opts.fetch,
+			 N_("fetch from the remote first if <start-point> is a remote-tracking branch")),
 		OPT_END()
 	};
 
@@ -2102,6 +2144,8 @@ int cmd_switch(int argc,
 			 N_("second guess 'git switch <no-such-branch>'")),
 		OPT_BOOL(0, "discard-changes", &opts.discard_changes,
 			 N_("throw away local modifications")),
+		OPT_BOOL(0, "fetch", &opts.fetch,
+			 N_("fetch from the remote first if <start-point> is a remote-tracking branch")),
 		OPT_END()
 	};
 
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 9bcf7c0b40..f5729f0831 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -801,4 +801,55 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
 	test_cmp_config "" --default "" branch.main2.merge
 '
 
+test_expect_success 'setup upstream for --fetch tests' '
+	git checkout main &&
+	git init fetch_upstream &&
+	test_commit -C fetch_upstream u_main &&
+	git remote add fetch_upstream fetch_upstream &&
+	git fetch fetch_upstream &&
+	git -C fetch_upstream checkout -b fetch_new &&
+	test_commit -C fetch_upstream u_new
+'
+
+test_expect_success 'checkout --fetch -b picks up branch created upstream after clone' '
+	git checkout main &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
+	git checkout --fetch -b local_new fetch_upstream/fetch_new &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD
+'
+
+test_expect_success 'checkout --fetch with bare remote name fetches the remote' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_new2 &&
+	test_commit -C fetch_upstream u_new2 &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2 &&
+	git checkout --fetch -b local_from_remote fetch_upstream &&
+	git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2
+'
+
+test_expect_success 'checkout --fetch aborts and does not create branch on fetch failure' '
+	git checkout main &&
+	test_might_fail git branch -D bogus &&
+	test_must_fail git checkout --fetch -b bogus fetch_upstream/does_not_exist &&
+	test_must_fail git rev-parse --verify refs/heads/bogus
+'
+
+test_expect_success 'checkout.fetch=true enables fetching without --fetch' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_cfg &&
+	test_commit -C fetch_upstream u_cfg &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_cfg &&
+	git -c checkout.fetch=true checkout -b local_cfg fetch_upstream/fetch_cfg &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_cfg HEAD
+'
+
+test_expect_success 'switch --fetch -c picks up branch created upstream after clone' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_switch &&
+	test_commit -C fetch_upstream u_switch &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
+	git switch --fetch -c local_switch fetch_upstream/fetch_switch &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
+'
+
 test_done
diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
index 2f9a597ec7..dc1d63669f 100755
--- a/t/t9902-completion.sh
+++ b/t/t9902-completion.sh
@@ -2602,6 +2602,7 @@ test_expect_success 'double dash "git checkout"' '
 	--ignore-other-worktrees Z
 	--recurse-submodules Z
 	--auto-advance Z
+	--fetch Z
 	--progress Z
 	--guess Z
 	--no-guess Z

base-commit: 94f057755b7941b321fd11fec1b2e3ca5313a4e0
-- 
gitgitgadget

[PATCH v3] checkout: add --fetch to fetch remote before resolving start-point

[Harald Nordgren via GitGitGadget]

From: Harald Nordgren <haraldnordgren@gmail.com>

A common workflow is:

    git fetch origin
    git checkout -b new_branch origin/some-branch

The first command exists purely so the second sees an up-to-date view
of the remote. If it is forgotten, origin/some-branch points at a stale
commit and the new local branch is created from the wrong start point.

Teach checkout (and switch) a --fetch flag that folds the two steps
into one:

    git checkout --fetch -b new_branch origin/some-branch

When --fetch is given and <start-point> is in <remote>/<branch> form,
run "git fetch <remote> <branch>" before resolving the ref. This
narrows the fetch to the requested branch so that other
remote-tracking branches are left untouched -- many tools rely on the
stability of remote-tracking refs between explicit fetches. If
<start-point> is a bare remote name like "origin" (which resolves to
that remote's default branch), "git fetch <remote>" is run instead,
since the target branch is not known up front. Abort the checkout if
the fetch fails.

Also add a checkout.fetch config to enable this by default.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
    checkout: add --fetch to fetch remote before resolving start-point
    
    When <start-point> is in <remote>/<branch> form, only fetch that one
    branch instead of the whole remote, so unrelated remote-tracking
    branches stay stable. The bare-remote form (e.g. "origin") still fetches
    everything.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2281%2FHaraldNordgren%2Fcheckout-fetch-start-point-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2281/HaraldNordgren/checkout-fetch-start-point-v3
Pull-Request: https://github.com/git/git/pull/2281

Range-diff vs v2:

 1:  13074c9fea ! 1:  df7b63862c checkout: add --fetch to fetch remote before resolving start-point
     @@ Commit message
      
              git checkout --fetch -b new_branch origin/some-branch
      
     -    When --fetch is given and <start-point> names a configured remote
     -    (either bare, like "origin", or prefixed, like "origin/foo"), fetch
     -    that remote before resolving the ref. Abort the checkout if the fetch
     -    fails.
     +    When --fetch is given and <start-point> is in <remote>/<branch> form,
     +    run "git fetch <remote> <branch>" before resolving the ref. This
     +    narrows the fetch to the requested branch so that other
     +    remote-tracking branches are left untouched -- many tools rely on the
     +    stability of remote-tracking refs between explicit fetches. If
     +    <start-point> is a bare remote name like "origin" (which resolves to
     +    that remote's default branch), "git fetch <remote>" is run instead,
     +    since the target branch is not known up front. Abort the checkout if
     +    the fetch fails.
      
          Also add a checkout.fetch config to enable this by default.
      
     @@ Documentation/git-checkout.adoc: linkgit:git-config[1].
       
      +`--fetch`::
      +`--no-fetch`::
     -+	If _<start-point>_ names a configured remote -- either bare,
     -+	like `origin` (which resolves to the remote's default branch),
     -+	or in _<remote>/<branch>_ form -- run `git fetch` on that
     -+	remote before resolving _<start-point>_. If the fetch fails,
     -+	the checkout is aborted and no local branch is created.
     ++	If _<start-point>_ refers to a remote-tracking branch, fetch
     ++	from that remote before resolving it. When _<start-point>_ is
     ++	in _<remote>/<branch>_ form, only that branch is updated; when
     ++	it is a bare remote name (e.g. `origin`), the whole remote is
     ++	fetched. If the fetch fails, the checkout is aborted.
      ++
      +The default behavior can be set via the `checkout.fetch` configuration
      +variable.
     @@ Documentation/git-switch.adoc: ambiguous but exists on the 'origin' remote. See
       
      +`--fetch`::
      +`--no-fetch`::
     -+	If _<start-point>_ names a configured remote -- either bare,
     -+	like `origin` (which resolves to the remote's default branch),
     -+	or in _<remote>/<branch>_ form -- run `git fetch` on that
     -+	remote before resolving _<start-point>_. If the fetch fails,
     -+	the switch is aborted and no local branch is created.
     ++	If _<start-point>_ refers to a remote-tracking branch, fetch
     ++	from that remote before resolving it. When _<start-point>_ is
     ++	in _<remote>/<branch>_ form, only that branch is updated; when
     ++	it is a bare remote name (e.g. `origin`), the whole remote is
     ++	fetched. If the fetch fails, the switch is aborted.
      ++
      +The default behavior can be set via the `checkout.fetch` configuration
      +variable.
     @@ builtin/checkout.c: struct branch_info {
      +	}
      +
      +	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
     ++	if (slash && slash[1])
     ++		strvec_push(&cmd.args, slash + 1);
      +	cmd.git_cmd = 1;
      +	free(remote_name);
      +	if (run_command(&cmd))
     @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh
      +	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD
      +'
      +
     ++test_expect_success 'checkout --fetch <remote>/<branch> leaves other tracking branches untouched' '
     ++	git checkout main &&
     ++	git -C fetch_upstream checkout -b fetch_target &&
     ++	test_commit -C fetch_upstream u_target_pre &&
     ++	git -C fetch_upstream checkout -b fetch_other &&
     ++	test_commit -C fetch_upstream u_other_pre &&
     ++	git fetch fetch_upstream &&
     ++	other_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_other) &&
     ++	git -C fetch_upstream checkout fetch_target &&
     ++	test_commit -C fetch_upstream u_target_post &&
     ++	git -C fetch_upstream checkout fetch_other &&
     ++	test_commit -C fetch_upstream u_other_post &&
     ++	git checkout --fetch -b local_target fetch_upstream/fetch_target &&
     ++	test_cmp_rev refs/remotes/fetch_upstream/fetch_target HEAD &&
     ++	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before"
     ++'
     ++
      +test_expect_success 'checkout --fetch with bare remote name fetches the remote' '
      +	git checkout main &&
      +	git -C fetch_upstream checkout -b fetch_new2 &&


 Documentation/config/checkout.adoc |  5 +++
 Documentation/git-checkout.adoc    | 11 +++++
 Documentation/git-switch.adoc      | 11 +++++
 builtin/checkout.c                 | 50 +++++++++++++++++++++-
 t/t7201-co.sh                      | 68 ++++++++++++++++++++++++++++++
 t/t9902-completion.sh              |  1 +
 6 files changed, 144 insertions(+), 2 deletions(-)

diff --git a/Documentation/config/checkout.adoc b/Documentation/config/checkout.adoc
index e35d212969..c95f72b38e 100644
--- a/Documentation/config/checkout.adoc
+++ b/Documentation/config/checkout.adoc
@@ -22,6 +22,11 @@ commands or functionality in the future.
 	option in `git checkout` and `git switch`. See
 	linkgit:git-switch[1] and linkgit:git-checkout[1].
 
+`checkout.fetch`::
+	Provides the default value for the `--fetch` or `--no-fetch`
+	option in `git checkout` and `git switch`. See
+	linkgit:git-switch[1] and linkgit:git-checkout[1].
+
 `checkout.workers`::
 	The number of parallel workers to use when updating the working tree.
 	The default is one, i.e. sequential execution. If set to a value less
diff --git a/Documentation/git-checkout.adoc b/Documentation/git-checkout.adoc
index 43ccf47cf6..f5cc1ced74 100644
--- a/Documentation/git-checkout.adoc
+++ b/Documentation/git-checkout.adoc
@@ -201,6 +201,17 @@ linkgit:git-config[1].
 The default behavior can be set via the `checkout.guess` configuration
 variable.
 
+`--fetch`::
+`--no-fetch`::
+	If _<start-point>_ refers to a remote-tracking branch, fetch
+	from that remote before resolving it. When _<start-point>_ is
+	in _<remote>/<branch>_ form, only that branch is updated; when
+	it is a bare remote name (e.g. `origin`), the whole remote is
+	fetched. If the fetch fails, the checkout is aborted.
++
+The default behavior can be set via the `checkout.fetch` configuration
+variable.
+
 `-l`::
 	Create the new branch's reflog; see linkgit:git-branch[1] for
 	details.
diff --git a/Documentation/git-switch.adoc b/Documentation/git-switch.adoc
index 87707e9265..29743bafea 100644
--- a/Documentation/git-switch.adoc
+++ b/Documentation/git-switch.adoc
@@ -110,6 +110,17 @@ ambiguous but exists on the 'origin' remote. See also
 The default behavior can be set via the `checkout.guess` configuration
 variable.
 
+`--fetch`::
+`--no-fetch`::
+	If _<start-point>_ refers to a remote-tracking branch, fetch
+	from that remote before resolving it. When _<start-point>_ is
+	in _<remote>/<branch>_ form, only that branch is updated; when
+	it is a bare remote name (e.g. `origin`), the whole remote is
+	fetched. If the fetch fails, the switch is aborted.
++
+The default behavior can be set via the `checkout.fetch` configuration
+variable.
+
 `-f`::
 `--force`::
 	An alias for `--discard-changes`.
diff --git a/builtin/checkout.c b/builtin/checkout.c
index e031e61886..8d810fe2fa 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -30,7 +30,9 @@
 #include "repo-settings.h"
 #include "resolve-undo.h"
 #include "revision.h"
+#include "run-command.h"
 #include "setup.h"
+#include "strvec.h"
 #include "submodule.h"
 #include "symlinks.h"
 #include "trace2.h"
@@ -61,6 +63,7 @@ struct checkout_opts {
 	int count_checkout_paths;
 	int overlay_mode;
 	int dwim_new_local_branch;
+	int fetch;
 	int discard_changes;
 	int accept_ref;
 	int accept_pathspec;
@@ -112,6 +115,36 @@ struct branch_info {
 	char *checkout;
 };
 
+static void fetch_remote_for_start_point(const char *arg)
+{
+	const char *slash;
+	char *remote_name;
+	struct remote *remote;
+	struct child_process cmd = CHILD_PROCESS_INIT;
+
+	if (!arg || !*arg)
+		return;
+
+	slash = strchr(arg, '/');
+	if (slash == arg)
+		return;
+	remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
+
+	remote = remote_get(remote_name);
+	if (!remote || !remote_is_configured(remote, 1)) {
+		free(remote_name);
+		return;
+	}
+
+	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
+	if (slash && slash[1])
+		strvec_push(&cmd.args, slash + 1);
+	cmd.git_cmd = 1;
+	free(remote_name);
+	if (run_command(&cmd))
+		die(_("failed to fetch start-point '%s'"), arg);
+}
+
 static void branch_info_release(struct branch_info *info)
 {
 	free(info->name);
@@ -1237,6 +1270,10 @@ static int git_checkout_config(const char *var, const char *value,
 		opts->dwim_new_local_branch = git_config_bool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "checkout.fetch")) {
+		opts->fetch = git_config_bool(var, value);
+		return 0;
+	}
 
 	if (starts_with(var, "submodule."))
 		return git_default_submodule_config(var, value, NULL);
@@ -1942,8 +1979,13 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 			opts->dwim_new_local_branch &&
 			opts->track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts->new_branch;
-		int n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
-					     &new_branch_info, opts, &rev);
+		int n;
+
+		if (opts->fetch)
+			fetch_remote_for_start_point(argv[0]);
+
+		n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
+					 &new_branch_info, opts, &rev);
 		argv += n;
 		argc -= n;
 	} else if (!opts->accept_ref && opts->from_treeish) {
@@ -2052,6 +2094,8 @@ int cmd_checkout(int argc,
 		OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode (default)")),
 		OPT_BOOL(0, "auto-advance", &opts.auto_advance,
 			 N_("auto advance to the next file when selecting hunks interactively")),
+		OPT_BOOL(0, "fetch", &opts.fetch,
+			 N_("fetch from the remote first if <start-point> is a remote-tracking branch")),
 		OPT_END()
 	};
 
@@ -2102,6 +2146,8 @@ int cmd_switch(int argc,
 			 N_("second guess 'git switch <no-such-branch>'")),
 		OPT_BOOL(0, "discard-changes", &opts.discard_changes,
 			 N_("throw away local modifications")),
+		OPT_BOOL(0, "fetch", &opts.fetch,
+			 N_("fetch from the remote first if <start-point> is a remote-tracking branch")),
 		OPT_END()
 	};
 
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 9bcf7c0b40..cf2ceb4052 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -801,4 +801,72 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
 	test_cmp_config "" --default "" branch.main2.merge
 '
 
+test_expect_success 'setup upstream for --fetch tests' '
+	git checkout main &&
+	git init fetch_upstream &&
+	test_commit -C fetch_upstream u_main &&
+	git remote add fetch_upstream fetch_upstream &&
+	git fetch fetch_upstream &&
+	git -C fetch_upstream checkout -b fetch_new &&
+	test_commit -C fetch_upstream u_new
+'
+
+test_expect_success 'checkout --fetch -b picks up branch created upstream after clone' '
+	git checkout main &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
+	git checkout --fetch -b local_new fetch_upstream/fetch_new &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD
+'
+
+test_expect_success 'checkout --fetch <remote>/<branch> leaves other tracking branches untouched' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_target &&
+	test_commit -C fetch_upstream u_target_pre &&
+	git -C fetch_upstream checkout -b fetch_other &&
+	test_commit -C fetch_upstream u_other_pre &&
+	git fetch fetch_upstream &&
+	other_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_other) &&
+	git -C fetch_upstream checkout fetch_target &&
+	test_commit -C fetch_upstream u_target_post &&
+	git -C fetch_upstream checkout fetch_other &&
+	test_commit -C fetch_upstream u_other_post &&
+	git checkout --fetch -b local_target fetch_upstream/fetch_target &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_target HEAD &&
+	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before"
+'
+
+test_expect_success 'checkout --fetch with bare remote name fetches the remote' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_new2 &&
+	test_commit -C fetch_upstream u_new2 &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2 &&
+	git checkout --fetch -b local_from_remote fetch_upstream &&
+	git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2
+'
+
+test_expect_success 'checkout --fetch aborts and does not create branch on fetch failure' '
+	git checkout main &&
+	test_might_fail git branch -D bogus &&
+	test_must_fail git checkout --fetch -b bogus fetch_upstream/does_not_exist &&
+	test_must_fail git rev-parse --verify refs/heads/bogus
+'
+
+test_expect_success 'checkout.fetch=true enables fetching without --fetch' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_cfg &&
+	test_commit -C fetch_upstream u_cfg &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_cfg &&
+	git -c checkout.fetch=true checkout -b local_cfg fetch_upstream/fetch_cfg &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_cfg HEAD
+'
+
+test_expect_success 'switch --fetch -c picks up branch created upstream after clone' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_switch &&
+	test_commit -C fetch_upstream u_switch &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
+	git switch --fetch -c local_switch fetch_upstream/fetch_switch &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
+'
+
 test_done
diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
index 2f9a597ec7..dc1d63669f 100755
--- a/t/t9902-completion.sh
+++ b/t/t9902-completion.sh
@@ -2602,6 +2602,7 @@ test_expect_success 'double dash "git checkout"' '
 	--ignore-other-worktrees Z
 	--recurse-submodules Z
 	--auto-advance Z
+	--fetch Z
 	--progress Z
 	--guess Z
 	--no-guess Z

base-commit: 94f057755b7941b321fd11fec1b2e3ca5313a4e0
-- 
gitgitgadget

Re: [PATCH v3] checkout: add --fetch to fetch remote before resolving start-point

[Ramsay Jones]

On 26/04/2026 8:24 am, Harald Nordgren via GitGitGadget wrote:
> From: Harald Nordgren <haraldnordgren@gmail.com>
> 
[snip]

> diff --git a/t/t7201-co.sh b/t/t7201-co.sh
> index 9bcf7c0b40..cf2ceb4052 100755
> --- a/t/t7201-co.sh
> +++ b/t/t7201-co.sh
> @@ -801,4 +801,72 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
>  	test_cmp_config "" --default "" branch.main2.merge
>  '
>  
> +test_expect_success 'setup upstream for --fetch tests' '
> +	git checkout main &&
> +	git init fetch_upstream &&
> +	test_commit -C fetch_upstream u_main &&
> +	git remote add fetch_upstream fetch_upstream &&
> +	git fetch fetch_upstream &&
> +	git -C fetch_upstream checkout -b fetch_new &&
> +	test_commit -C fetch_upstream u_new
> +'
> +
> +test_expect_success 'checkout --fetch -b picks up branch created upstream after clone' '
> +	git checkout main &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
> +	git checkout --fetch -b local_new fetch_upstream/fetch_new &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD
> +'
> +
> +test_expect_success 'checkout --fetch <remote>/<branch> leaves other tracking branches untouched' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_target &&
> +	test_commit -C fetch_upstream u_target_pre &&
> +	git -C fetch_upstream checkout -b fetch_other &&
> +	test_commit -C fetch_upstream u_other_pre &&
> +	git fetch fetch_upstream &&
> +	other_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_other) &&
> +	git -C fetch_upstream checkout fetch_target &&
> +	test_commit -C fetch_upstream u_target_post &&
> +	git -C fetch_upstream checkout fetch_other &&
> +	test_commit -C fetch_upstream u_other_post &&
> +	git checkout --fetch -b local_target fetch_upstream/fetch_target &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_target HEAD &&
> +	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before"
> +'
> +
> +test_expect_success 'checkout --fetch with bare remote name fetches the remote' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_new2 &&
> +	test_commit -C fetch_upstream u_new2 &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2 &&
> +	git checkout --fetch -b local_from_remote fetch_upstream &&
> +	git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2
> +'
> +
> +test_expect_success 'checkout --fetch aborts and does not create branch on fetch failure' '
> +	git checkout main &&
> +	test_might_fail git branch -D bogus &&
> +	test_must_fail git checkout --fetch -b bogus fetch_upstream/does_not_exist &&
> +	test_must_fail git rev-parse --verify refs/heads/bogus
> +'
> +
> +test_expect_success 'checkout.fetch=true enables fetching without --fetch' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_cfg &&
> +	test_commit -C fetch_upstream u_cfg &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_cfg &&
> +	git -c checkout.fetch=true checkout -b local_cfg fetch_upstream/fetch_cfg &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_cfg HEAD
> +'
> +
> +test_expect_success 'switch --fetch -c picks up branch created upstream after clone' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_switch &&
> +	test_commit -C fetch_upstream u_switch &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
> +	git switch --fetch -c local_switch fetch_upstream/fetch_switch &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
> +'
> +
>  test_done

Still just skimming the list, so ... ;)

I seem to have missed v2 (but I guess the config name changed in v2), but it seems
that there is still no test that confirms '--no-fetch' can countermand the config
variable (or, indeed, an earlier command-line '--fetch' etc,.).

[I would have no use for this facility (I have _never_ used git-pull for similar
reasons) since I would find it odd to 'mash' git-fetch into git-checkout/switch! :) ]

ATB,
Ramsay Jones

[PATCH v4] checkout: add --fetch to fetch remote before resolving start-point

[Harald Nordgren via GitGitGadget]

From: Harald Nordgren <haraldnordgren@gmail.com>

A common workflow is:

    git fetch origin
    git checkout -b new_branch origin/some-branch

The first command exists purely so the second sees an up-to-date view
of the remote. If it is forgotten, origin/some-branch points at a stale
commit and the new local branch is created from the wrong start point.

Teach checkout (and switch) a --fetch flag that folds the two steps
into one:

    git checkout --fetch -b new_branch origin/some-branch

When --fetch is given and <start-point> is in <remote>/<branch> form,
run "git fetch <remote> <branch>" before resolving the ref. This
narrows the fetch to the requested branch so that other
remote-tracking branches are left untouched -- many tools rely on the
stability of remote-tracking refs between explicit fetches. If
<start-point> is a bare remote name like "origin" (which resolves to
that remote's default branch), "git fetch <remote>" is run instead,
since the target branch is not known up front. Abort the checkout if
the fetch fails.

Also add a checkout.fetch config to enable this by default.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
    checkout: add --fetch to fetch remote before resolving start-point
    
    Adding tests to confirm that '--no-fetch' can countermand the config.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2281%2FHaraldNordgren%2Fcheckout-fetch-start-point-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2281/HaraldNordgren/checkout-fetch-start-point-v4
Pull-Request: https://github.com/git/git/pull/2281

Range-diff vs v3:

 1:  df7b63862c ! 1:  150ccbb621 checkout: add --fetch to fetch remote before resolving start-point
     @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh
      +	test_cmp_rev refs/remotes/fetch_upstream/fetch_cfg HEAD
      +'
      +
     ++test_expect_success '--no-fetch overrides checkout.fetch=true' '
     ++	git checkout main &&
     ++	git -C fetch_upstream checkout -b fetch_nofetch &&
     ++	test_commit -C fetch_upstream u_nofetch &&
     ++	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_nofetch &&
     ++	test_must_fail git -c checkout.fetch=true checkout --no-fetch \
     ++		-b local_nofetch fetch_upstream/fetch_nofetch &&
     ++	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_nofetch &&
     ++	test_must_fail git rev-parse --verify refs/heads/local_nofetch
     ++'
     ++
     ++test_expect_success '--no-fetch overrides earlier --fetch on command line' '
     ++	git checkout main &&
     ++	git -C fetch_upstream checkout -b fetch_override &&
     ++	test_commit -C fetch_upstream u_override &&
     ++	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_override &&
     ++	test_must_fail git checkout --fetch --no-fetch \
     ++		-b local_override fetch_upstream/fetch_override &&
     ++	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_override &&
     ++	test_must_fail git rev-parse --verify refs/heads/local_override
     ++'
     ++
      +test_expect_success 'switch --fetch -c picks up branch created upstream after clone' '
      +	git checkout main &&
      +	git -C fetch_upstream checkout -b fetch_switch &&


 Documentation/config/checkout.adoc |  5 ++
 Documentation/git-checkout.adoc    | 11 ++++
 Documentation/git-switch.adoc      | 11 ++++
 builtin/checkout.c                 | 50 ++++++++++++++++-
 t/t7201-co.sh                      | 90 ++++++++++++++++++++++++++++++
 t/t9902-completion.sh              |  1 +
 6 files changed, 166 insertions(+), 2 deletions(-)

diff --git a/Documentation/config/checkout.adoc b/Documentation/config/checkout.adoc
index e35d212969..c95f72b38e 100644
--- a/Documentation/config/checkout.adoc
+++ b/Documentation/config/checkout.adoc
@@ -22,6 +22,11 @@ commands or functionality in the future.
 	option in `git checkout` and `git switch`. See
 	linkgit:git-switch[1] and linkgit:git-checkout[1].
 
+`checkout.fetch`::
+	Provides the default value for the `--fetch` or `--no-fetch`
+	option in `git checkout` and `git switch`. See
+	linkgit:git-switch[1] and linkgit:git-checkout[1].
+
 `checkout.workers`::
 	The number of parallel workers to use when updating the working tree.
 	The default is one, i.e. sequential execution. If set to a value less
diff --git a/Documentation/git-checkout.adoc b/Documentation/git-checkout.adoc
index 43ccf47cf6..f5cc1ced74 100644
--- a/Documentation/git-checkout.adoc
+++ b/Documentation/git-checkout.adoc
@@ -201,6 +201,17 @@ linkgit:git-config[1].
 The default behavior can be set via the `checkout.guess` configuration
 variable.
 
+`--fetch`::
+`--no-fetch`::
+	If _<start-point>_ refers to a remote-tracking branch, fetch
+	from that remote before resolving it. When _<start-point>_ is
+	in _<remote>/<branch>_ form, only that branch is updated; when
+	it is a bare remote name (e.g. `origin`), the whole remote is
+	fetched. If the fetch fails, the checkout is aborted.
++
+The default behavior can be set via the `checkout.fetch` configuration
+variable.
+
 `-l`::
 	Create the new branch's reflog; see linkgit:git-branch[1] for
 	details.
diff --git a/Documentation/git-switch.adoc b/Documentation/git-switch.adoc
index 87707e9265..29743bafea 100644
--- a/Documentation/git-switch.adoc
+++ b/Documentation/git-switch.adoc
@@ -110,6 +110,17 @@ ambiguous but exists on the 'origin' remote. See also
 The default behavior can be set via the `checkout.guess` configuration
 variable.
 
+`--fetch`::
+`--no-fetch`::
+	If _<start-point>_ refers to a remote-tracking branch, fetch
+	from that remote before resolving it. When _<start-point>_ is
+	in _<remote>/<branch>_ form, only that branch is updated; when
+	it is a bare remote name (e.g. `origin`), the whole remote is
+	fetched. If the fetch fails, the switch is aborted.
++
+The default behavior can be set via the `checkout.fetch` configuration
+variable.
+
 `-f`::
 `--force`::
 	An alias for `--discard-changes`.
diff --git a/builtin/checkout.c b/builtin/checkout.c
index e031e61886..8d810fe2fa 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -30,7 +30,9 @@
 #include "repo-settings.h"
 #include "resolve-undo.h"
 #include "revision.h"
+#include "run-command.h"
 #include "setup.h"
+#include "strvec.h"
 #include "submodule.h"
 #include "symlinks.h"
 #include "trace2.h"
@@ -61,6 +63,7 @@ struct checkout_opts {
 	int count_checkout_paths;
 	int overlay_mode;
 	int dwim_new_local_branch;
+	int fetch;
 	int discard_changes;
 	int accept_ref;
 	int accept_pathspec;
@@ -112,6 +115,36 @@ struct branch_info {
 	char *checkout;
 };
 
+static void fetch_remote_for_start_point(const char *arg)
+{
+	const char *slash;
+	char *remote_name;
+	struct remote *remote;
+	struct child_process cmd = CHILD_PROCESS_INIT;
+
+	if (!arg || !*arg)
+		return;
+
+	slash = strchr(arg, '/');
+	if (slash == arg)
+		return;
+	remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
+
+	remote = remote_get(remote_name);
+	if (!remote || !remote_is_configured(remote, 1)) {
+		free(remote_name);
+		return;
+	}
+
+	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
+	if (slash && slash[1])
+		strvec_push(&cmd.args, slash + 1);
+	cmd.git_cmd = 1;
+	free(remote_name);
+	if (run_command(&cmd))
+		die(_("failed to fetch start-point '%s'"), arg);
+}
+
 static void branch_info_release(struct branch_info *info)
 {
 	free(info->name);
@@ -1237,6 +1270,10 @@ static int git_checkout_config(const char *var, const char *value,
 		opts->dwim_new_local_branch = git_config_bool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "checkout.fetch")) {
+		opts->fetch = git_config_bool(var, value);
+		return 0;
+	}
 
 	if (starts_with(var, "submodule."))
 		return git_default_submodule_config(var, value, NULL);
@@ -1942,8 +1979,13 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 			opts->dwim_new_local_branch &&
 			opts->track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts->new_branch;
-		int n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
-					     &new_branch_info, opts, &rev);
+		int n;
+
+		if (opts->fetch)
+			fetch_remote_for_start_point(argv[0]);
+
+		n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
+					 &new_branch_info, opts, &rev);
 		argv += n;
 		argc -= n;
 	} else if (!opts->accept_ref && opts->from_treeish) {
@@ -2052,6 +2094,8 @@ int cmd_checkout(int argc,
 		OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode (default)")),
 		OPT_BOOL(0, "auto-advance", &opts.auto_advance,
 			 N_("auto advance to the next file when selecting hunks interactively")),
+		OPT_BOOL(0, "fetch", &opts.fetch,
+			 N_("fetch from the remote first if <start-point> is a remote-tracking branch")),
 		OPT_END()
 	};
 
@@ -2102,6 +2146,8 @@ int cmd_switch(int argc,
 			 N_("second guess 'git switch <no-such-branch>'")),
 		OPT_BOOL(0, "discard-changes", &opts.discard_changes,
 			 N_("throw away local modifications")),
+		OPT_BOOL(0, "fetch", &opts.fetch,
+			 N_("fetch from the remote first if <start-point> is a remote-tracking branch")),
 		OPT_END()
 	};
 
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 9bcf7c0b40..731be2680a 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -801,4 +801,94 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
 	test_cmp_config "" --default "" branch.main2.merge
 '
 
+test_expect_success 'setup upstream for --fetch tests' '
+	git checkout main &&
+	git init fetch_upstream &&
+	test_commit -C fetch_upstream u_main &&
+	git remote add fetch_upstream fetch_upstream &&
+	git fetch fetch_upstream &&
+	git -C fetch_upstream checkout -b fetch_new &&
+	test_commit -C fetch_upstream u_new
+'
+
+test_expect_success 'checkout --fetch -b picks up branch created upstream after clone' '
+	git checkout main &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
+	git checkout --fetch -b local_new fetch_upstream/fetch_new &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD
+'
+
+test_expect_success 'checkout --fetch <remote>/<branch> leaves other tracking branches untouched' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_target &&
+	test_commit -C fetch_upstream u_target_pre &&
+	git -C fetch_upstream checkout -b fetch_other &&
+	test_commit -C fetch_upstream u_other_pre &&
+	git fetch fetch_upstream &&
+	other_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_other) &&
+	git -C fetch_upstream checkout fetch_target &&
+	test_commit -C fetch_upstream u_target_post &&
+	git -C fetch_upstream checkout fetch_other &&
+	test_commit -C fetch_upstream u_other_post &&
+	git checkout --fetch -b local_target fetch_upstream/fetch_target &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_target HEAD &&
+	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before"
+'
+
+test_expect_success 'checkout --fetch with bare remote name fetches the remote' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_new2 &&
+	test_commit -C fetch_upstream u_new2 &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2 &&
+	git checkout --fetch -b local_from_remote fetch_upstream &&
+	git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2
+'
+
+test_expect_success 'checkout --fetch aborts and does not create branch on fetch failure' '
+	git checkout main &&
+	test_might_fail git branch -D bogus &&
+	test_must_fail git checkout --fetch -b bogus fetch_upstream/does_not_exist &&
+	test_must_fail git rev-parse --verify refs/heads/bogus
+'
+
+test_expect_success 'checkout.fetch=true enables fetching without --fetch' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_cfg &&
+	test_commit -C fetch_upstream u_cfg &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_cfg &&
+	git -c checkout.fetch=true checkout -b local_cfg fetch_upstream/fetch_cfg &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_cfg HEAD
+'
+
+test_expect_success '--no-fetch overrides checkout.fetch=true' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_nofetch &&
+	test_commit -C fetch_upstream u_nofetch &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_nofetch &&
+	test_must_fail git -c checkout.fetch=true checkout --no-fetch \
+		-b local_nofetch fetch_upstream/fetch_nofetch &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_nofetch &&
+	test_must_fail git rev-parse --verify refs/heads/local_nofetch
+'
+
+test_expect_success '--no-fetch overrides earlier --fetch on command line' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_override &&
+	test_commit -C fetch_upstream u_override &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_override &&
+	test_must_fail git checkout --fetch --no-fetch \
+		-b local_override fetch_upstream/fetch_override &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_override &&
+	test_must_fail git rev-parse --verify refs/heads/local_override
+'
+
+test_expect_success 'switch --fetch -c picks up branch created upstream after clone' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_switch &&
+	test_commit -C fetch_upstream u_switch &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
+	git switch --fetch -c local_switch fetch_upstream/fetch_switch &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
+'
+
 test_done
diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
index 2f9a597ec7..dc1d63669f 100755
--- a/t/t9902-completion.sh
+++ b/t/t9902-completion.sh
@@ -2602,6 +2602,7 @@ test_expect_success 'double dash "git checkout"' '
 	--ignore-other-worktrees Z
 	--recurse-submodules Z
 	--auto-advance Z
+	--fetch Z
 	--progress Z
 	--guess Z
 	--no-guess Z

base-commit: 94f057755b7941b321fd11fec1b2e3ca5313a4e0
-- 
gitgitgadget

Re: [PATCH v4] checkout: add --fetch to fetch remote before resolving start-point

[Junio C Hamano]

"Harald Nordgren via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Harald Nordgren <haraldnordgren@gmail.com>

> A common workflow is:
>
>     git fetch origin
>     git checkout -b new_branch origin/some-branch
>
> The first command exists purely so the second sees an up-to-date view
> of the remote.

This is only half true, isn't it?

Git is among projects that encourage forking only from a well-known
point in history (like the latest released version), not at a random
"tip of the day" commit from the upstream.

Such projects also tend to discourage people from constantly pulling
updated upstream into their unfinished topic branch, or rebase their
unfinished topic branch on top of updated upstream, only to "catch
up", and instead encourage them to make a trial merge to notice when
the base got too stale to cause eventual merge to conflict too much,
and when it happens, make such a back-merge, but otherwise keep
working on the stable base and avoid such "catching up".

And when working with such a project, what users who do the above is
forgetting is to inspect origin/master between the two steps to see
if it is a good commit to start your topic at.

> If it is forgotten, origin/some-branch points at a stale commit
> and the new local branch is created from the wrong start point.

So this part is not quite true.  What makes your topic begin at a
wrong starting point is not that you forget to fetch, but you forget
to verify what you fetched and think if it is a good starting point.

And for that verification to happen, you do not want "checkout" and
"fetch" mixed into one.

On the other hand, if you are allowed to fork at anywhere (as
opposed to a latest release), then not fetching and building on top
of slightly older codebase is not such a huge deal, as you're likely
to be making the "catch up" changes on top of your unfinished work
later anyway.

So as I already said before, I am fairly negative on this topic.  It
feels more like a knob to allow and actively encourage people to be
more sloppy than anything else.

I may have already pointed this out (but I do not remember), but
this option would not make any sense when --track is not in effect,
so instead of adding a brand new option, making it an extension to
the existing --track option might make it slightly more palatable.

Re: [PATCH] checkout: add --fetch to fetch remote before resolving start-point

[Harald Nordgren]

I hope you had a good leave and is back with renewed energy! ☀️

> Git is among projects that encourage forking only from a well-known
> point in history (like the latest released version), not at a random
> "tip of the day" commit from the upstream.

Are you talking about the Git project that we are working on right now, or
talking about how people use Git "in the wild"?

Because how people use Git in the wild can be a bit different, and merge
conflicts arguably the worst part of collaborating with a team using Git.
In my early days as a professional coder, snubbed my toe countless times on
forgetting to pull in the latest changes, before starting to work on
something.

I respect that things work differently in a neatly ordered project like Git
itself, where you do a great work of organizing, but all other projects are
not like that. My advice to a junior developer is to pull in the latest
changes when starting and to rebase obsessively to prevent a large merge
conflict down the road.

> So instead of introducing a totally new option that can only be used
> only when "--track" is given, it might make more sense to introduce
> this as a variant of "--track", perhaps "--track=fetch,[in]direct"
> or something like that. 

> I may have already pointed this out (but I do not remember), but
> this option would not make any sense when --track is not in effect,
> so instead of adding a brand new option, making it an extension to
> the existing --track option might make it slightly more palatable.

Fair enough. You did point it out and I will give that a try!


Harald

[PATCH v5] checkout: extend --track with a "fetch" mode to refresh start-point

[Harald Nordgren via GitGitGadget]

From: Harald Nordgren <haraldnordgren@gmail.com>

A common workflow is:

    git fetch origin
    git checkout -b new_branch --track origin/some-branch

The first command exists so the second sees an up-to-date view of the
remote. If it is forgotten, origin/some-branch points at a stale
commit and the new local branch is created from the wrong start
point. This only matters when the user is setting up tracking and
expects the new branch to start at the freshest tip; for a one-off
checkout of an arbitrary commit there is no reason to "freshen" the
start-point.

Tie the new behavior to --track for that reason: extend its argument
to take a comma-separated list, where "fetch" can be combined with the
existing "direct" (default) and "inherit" modes. Examples:

    git checkout --track=fetch -b new_branch origin/some-branch
    git checkout --track=fetch,inherit -b new_branch some_local_branch
    git switch --track=fetch -c new_branch origin/some-branch

When "fetch" is requested and <start-point> is in <remote>/<branch>
form, run "git fetch <remote> <branch>" before resolving the ref. This
narrows the fetch to the requested branch so that other
remote-tracking branches are left untouched -- many tools rely on the
stability of remote-tracking refs between explicit fetches. If
<start-point> is a bare remote name like "origin" (which resolves to
that remote's default branch), "git fetch <remote>" is run instead,
since the target branch is not known up front. Abort the checkout if
the fetch fails.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
    checkout: add --fetch to fetch remote before resolving start-point
    
     * Folded --fetch into --track. The standalone --fetch/--no-fetch flags
       are gone; the same behavior is now requested via --track=fetch
       (combinable as --track=fetch,inherit).
     * Removed the checkout.fetch config. Since fetching is tied to --track,
       there's no separate config knob anymore.
     * Docs reworked accordingly. --track's syntax is now
       (direct|inherit|fetch)[,...] in both git-checkout and git-switch man
       pages, with the fetch behavior described under it. The old --fetch
       and checkout.fetch sections are deleted.
     * New parser callback in checkout.c. A small parse_opt_checkout_track
       splits the comma-separated argument with string_list_split and sets
       opts->track and opts->fetch together.
     * Tests updated and trimmed. All test invocations switched from --fetch
       to --track=fetch. Dropped the checkout.fetch=true and --no-fetch
       override tests (those features no longer exist). Added a
       --track=fetch,inherit test, a --track=bogus error test, and stronger
       config-assertion checks on the basic test. Two redundant tests
       (fetch,direct and order-insensitivity) were removed.
     * Completion list cleaned up. --fetch removed from the expected git
       checkout option list.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2281%2FHaraldNordgren%2Fcheckout-fetch-start-point-v5
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2281/HaraldNordgren/checkout-fetch-start-point-v5
Pull-Request: https://github.com/git/git/pull/2281

Range-diff vs v4:

 1:  150ccbb621 ! 1:  8ebc2f94b9 checkout: add --fetch to fetch remote before resolving start-point
     @@ Metadata
      Author: Harald Nordgren <haraldnordgren@gmail.com>
      
       ## Commit message ##
     -    checkout: add --fetch to fetch remote before resolving start-point
     +    checkout: extend --track with a "fetch" mode to refresh start-point
      
          A common workflow is:
      
              git fetch origin
     -        git checkout -b new_branch origin/some-branch
     +        git checkout -b new_branch --track origin/some-branch
      
     -    The first command exists purely so the second sees an up-to-date view
     -    of the remote. If it is forgotten, origin/some-branch points at a stale
     -    commit and the new local branch is created from the wrong start point.
     +    The first command exists so the second sees an up-to-date view of the
     +    remote. If it is forgotten, origin/some-branch points at a stale
     +    commit and the new local branch is created from the wrong start
     +    point. This only matters when the user is setting up tracking and
     +    expects the new branch to start at the freshest tip; for a one-off
     +    checkout of an arbitrary commit there is no reason to "freshen" the
     +    start-point.
      
     -    Teach checkout (and switch) a --fetch flag that folds the two steps
     -    into one:
     +    Tie the new behavior to --track for that reason: extend its argument
     +    to take a comma-separated list, where "fetch" can be combined with the
     +    existing "direct" (default) and "inherit" modes. Examples:
      
     -        git checkout --fetch -b new_branch origin/some-branch
     +        git checkout --track=fetch -b new_branch origin/some-branch
     +        git checkout --track=fetch,inherit -b new_branch some_local_branch
     +        git switch --track=fetch -c new_branch origin/some-branch
      
     -    When --fetch is given and <start-point> is in <remote>/<branch> form,
     -    run "git fetch <remote> <branch>" before resolving the ref. This
     +    When "fetch" is requested and <start-point> is in <remote>/<branch>
     +    form, run "git fetch <remote> <branch>" before resolving the ref. This
          narrows the fetch to the requested branch so that other
          remote-tracking branches are left untouched -- many tools rely on the
          stability of remote-tracking refs between explicit fetches. If
     @@ Commit message
          since the target branch is not known up front. Abort the checkout if
          the fetch fails.
      
     -    Also add a checkout.fetch config to enable this by default.
     -
          Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
      
     - ## Documentation/config/checkout.adoc ##
     -@@ Documentation/config/checkout.adoc: commands or functionality in the future.
     - 	option in `git checkout` and `git switch`. See
     - 	linkgit:git-switch[1] and linkgit:git-checkout[1].
     - 
     -+`checkout.fetch`::
     -+	Provides the default value for the `--fetch` or `--no-fetch`
     -+	option in `git checkout` and `git switch`. See
     -+	linkgit:git-switch[1] and linkgit:git-checkout[1].
     -+
     - `checkout.workers`::
     - 	The number of parallel workers to use when updating the working tree.
     - 	The default is one, i.e. sequential execution. If set to a value less
     -
       ## Documentation/git-checkout.adoc ##
     -@@ Documentation/git-checkout.adoc: linkgit:git-config[1].
     - The default behavior can be set via the `checkout.guess` configuration
     - variable.
     +@@ Documentation/git-checkout.adoc: of it").
     + 	resets _<branch>_ to the start point instead of failing.
       
     -+`--fetch`::
     -+`--no-fetch`::
     -+	If _<start-point>_ refers to a remote-tracking branch, fetch
     -+	from that remote before resolving it. When _<start-point>_ is
     -+	in _<remote>/<branch>_ form, only that branch is updated; when
     -+	it is a bare remote name (e.g. `origin`), the whole remote is
     -+	fetched. If the fetch fails, the checkout is aborted.
     + `-t`::
     +-`--track[=(direct|inherit)]`::
     ++`--track[=(direct|inherit|fetch)[,...]]`::
     + 	When creating a new branch, set up "upstream" configuration. See
     + 	`--track` in linkgit:git-branch[1] for details. As a convenience,
     + 	--track without -b implies branch creation.
     + +
     ++The argument is a comma-separated list. `direct` (the default) and
     ++`inherit` select the tracking mode. Adding `fetch` requests that the
     ++remote be fetched before _<start-point>_ is resolved, so the new branch
     ++starts from a fresh tip: when _<start-point>_ is in
     ++_<remote>/<branch>_ form, only that branch is updated; when it is a
     ++bare remote name (e.g. `origin`), the whole remote is fetched. If the
     ++fetch fails, the checkout is aborted.
      ++
     -+The default behavior can be set via the `checkout.fetch` configuration
     -+variable.
     -+
     - `-l`::
     - 	Create the new branch's reflog; see linkgit:git-branch[1] for
     - 	details.
     + If no `-b` option is given, the name of the new branch will be
     + derived from the remote-tracking branch, by looking at the local part of
     + the refspec configured for the corresponding remote, and then stripping
      
       ## Documentation/git-switch.adoc ##
     -@@ Documentation/git-switch.adoc: ambiguous but exists on the 'origin' remote. See also
     - The default behavior can be set via the `checkout.guess` configuration
     - variable.
     +@@ Documentation/git-switch.adoc: should result in deletion of the path).
     + 	attached to a terminal, regardless of `--quiet`.
       
     -+`--fetch`::
     -+`--no-fetch`::
     -+	If _<start-point>_ refers to a remote-tracking branch, fetch
     -+	from that remote before resolving it. When _<start-point>_ is
     -+	in _<remote>/<branch>_ form, only that branch is updated; when
     -+	it is a bare remote name (e.g. `origin`), the whole remote is
     -+	fetched. If the fetch fails, the switch is aborted.
     + `-t`::
     +-`--track[ (direct|inherit)]`::
     ++`--track[=(direct|inherit|fetch)[,...]]`::
     + 	When creating a new branch, set up "upstream" configuration.
     + 	`-c` is implied. See `--track` in linkgit:git-branch[1] for
     + 	details.
     + +
     ++The argument is a comma-separated list. `direct` (the default) and
     ++`inherit` select the tracking mode. Adding `fetch` requests that the
     ++remote be fetched before _<start-point>_ is resolved, so the new branch
     ++starts from a fresh tip: when _<start-point>_ is in
     ++_<remote>/<branch>_ form, only that branch is updated; when it is a
     ++bare remote name (e.g. `origin`), the whole remote is fetched. If the
     ++fetch fails, the switch is aborted.
      ++
     -+The default behavior can be set via the `checkout.fetch` configuration
     -+variable.
     -+
     - `-f`::
     - `--force`::
     - 	An alias for `--discard-changes`.
     + If no `-c` option is given, the name of the new branch will be derived
     + from the remote-tracking branch, by looking at the local part of the
     + refspec configured for the corresponding remote, and then stripping
      
       ## builtin/checkout.c ##
      @@
     @@ builtin/checkout.c: struct branch_info {
      +	if (run_command(&cmd))
      +		die(_("failed to fetch start-point '%s'"), arg);
      +}
     ++
     ++static int parse_opt_checkout_track(const struct option *opt,
     ++				    const char *arg, int unset)
     ++{
     ++	struct checkout_opts *opts = opt->value;
     ++	struct string_list tokens = STRING_LIST_INIT_DUP;
     ++	struct string_list_item *item;
     ++	int ret = 0;
     ++
     ++	if (unset) {
     ++		opts->track = BRANCH_TRACK_NEVER;
     ++		opts->fetch = 0;
     ++		return 0;
     ++	}
     ++
     ++	opts->track = BRANCH_TRACK_EXPLICIT;
     ++	if (!arg)
     ++		return 0;
     ++
     ++	string_list_split(&tokens, arg, ",", -1);
     ++	for_each_string_list_item(item, &tokens) {
     ++		if (!strcmp(item->string, "fetch")) {
     ++			opts->fetch = 1;
     ++		} else if (!strcmp(item->string, "direct")) {
     ++			opts->track = BRANCH_TRACK_EXPLICIT;
     ++		} else if (!strcmp(item->string, "inherit")) {
     ++			opts->track = BRANCH_TRACK_INHERIT;
     ++		} else {
     ++			ret = error(_("option `%s' expects \"%s\", \"%s\", "
     ++				      "or \"%s\""),
     ++				    "--track", "direct", "inherit", "fetch");
     ++			break;
     ++		}
     ++	}
     ++
     ++	string_list_clear(&tokens, 0);
     ++	return ret;
     ++}
      +
       static void branch_info_release(struct branch_info *info)
       {
     @@ builtin/checkout.c: static int git_checkout_config(const char *var, const char *
       		opts->dwim_new_local_branch = git_config_bool(var, value);
       		return 0;
       	}
     -+	if (!strcmp(var, "checkout.fetch")) {
     -+		opts->fetch = git_config_bool(var, value);
     -+		return 0;
     -+	}
     - 
     +-
       	if (starts_with(var, "submodule."))
       		return git_default_submodule_config(var, value, NULL);
     + 
     +@@ builtin/checkout.c: static struct option *add_common_switch_branch_options(
     + {
     + 	struct option options[] = {
     + 		OPT_BOOL('d', "detach", &opts->force_detach, N_("detach HEAD at named commit")),
     +-		OPT_CALLBACK_F('t', "track",  &opts->track, "(direct|inherit)",
     ++		OPT_CALLBACK_F('t', "track",  opts, "(direct|inherit|fetch)[,...]",
     + 			N_("set branch tracking configuration"),
     + 			PARSE_OPT_OPTARG,
     +-			parse_opt_tracking_mode),
     ++			parse_opt_checkout_track),
     + 		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
     + 			   PARSE_OPT_NOCOMPLETE),
     + 		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unborn branch")),
      @@ builtin/checkout.c: static int checkout_main(int argc, const char **argv, const char *prefix,
       			opts->dwim_new_local_branch &&
       			opts->track == BRANCH_TRACK_UNSPECIFIED &&
     @@ builtin/checkout.c: static int checkout_main(int argc, const char **argv, const
       		argv += n;
       		argc -= n;
       	} else if (!opts->accept_ref && opts->from_treeish) {
     -@@ builtin/checkout.c: int cmd_checkout(int argc,
     - 		OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode (default)")),
     - 		OPT_BOOL(0, "auto-advance", &opts.auto_advance,
     - 			 N_("auto advance to the next file when selecting hunks interactively")),
     -+		OPT_BOOL(0, "fetch", &opts.fetch,
     -+			 N_("fetch from the remote first if <start-point> is a remote-tracking branch")),
     - 		OPT_END()
     - 	};
     - 
     -@@ builtin/checkout.c: int cmd_switch(int argc,
     - 			 N_("second guess 'git switch <no-such-branch>'")),
     - 		OPT_BOOL(0, "discard-changes", &opts.discard_changes,
     - 			 N_("throw away local modifications")),
     -+		OPT_BOOL(0, "fetch", &opts.fetch,
     -+			 N_("fetch from the remote first if <start-point> is a remote-tracking branch")),
     - 		OPT_END()
     - 	};
     - 
      
       ## t/t7201-co.sh ##
      @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
       	test_cmp_config "" --default "" branch.main2.merge
       '
       
     -+test_expect_success 'setup upstream for --fetch tests' '
     ++test_expect_success 'setup upstream for --track=fetch tests' '
      +	git checkout main &&
      +	git init fetch_upstream &&
      +	test_commit -C fetch_upstream u_main &&
     @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh
      +	test_commit -C fetch_upstream u_new
      +'
      +
     -+test_expect_success 'checkout --fetch -b picks up branch created upstream after clone' '
     ++test_expect_success 'checkout --track=fetch -b picks up branch created upstream after clone' '
      +	git checkout main &&
      +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
     -+	git checkout --fetch -b local_new fetch_upstream/fetch_new &&
     -+	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD
     ++	git checkout --track=fetch -b local_new fetch_upstream/fetch_new &&
     ++	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD &&
     ++	test_cmp_config fetch_upstream branch.local_new.remote &&
     ++	test_cmp_config refs/heads/fetch_new branch.local_new.merge
      +'
      +
     -+test_expect_success 'checkout --fetch <remote>/<branch> leaves other tracking branches untouched' '
     ++test_expect_success 'checkout --track=fetch <remote>/<branch> leaves other tracking branches untouched' '
      +	git checkout main &&
      +	git -C fetch_upstream checkout -b fetch_target &&
      +	test_commit -C fetch_upstream u_target_pre &&
     @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh
      +	test_commit -C fetch_upstream u_target_post &&
      +	git -C fetch_upstream checkout fetch_other &&
      +	test_commit -C fetch_upstream u_other_post &&
     -+	git checkout --fetch -b local_target fetch_upstream/fetch_target &&
     ++	git checkout --track=fetch -b local_target fetch_upstream/fetch_target &&
      +	test_cmp_rev refs/remotes/fetch_upstream/fetch_target HEAD &&
      +	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before"
      +'
      +
     -+test_expect_success 'checkout --fetch with bare remote name fetches the remote' '
     ++test_expect_success 'checkout --track=fetch with bare remote name fetches the remote' '
      +	git checkout main &&
      +	git -C fetch_upstream checkout -b fetch_new2 &&
      +	test_commit -C fetch_upstream u_new2 &&
      +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2 &&
     -+	git checkout --fetch -b local_from_remote fetch_upstream &&
     ++	git checkout --track=fetch -b local_from_remote fetch_upstream &&
      +	git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2
      +'
      +
     -+test_expect_success 'checkout --fetch aborts and does not create branch on fetch failure' '
     ++test_expect_success 'checkout --track=fetch aborts and does not create branch on fetch failure' '
      +	git checkout main &&
      +	test_might_fail git branch -D bogus &&
     -+	test_must_fail git checkout --fetch -b bogus fetch_upstream/does_not_exist &&
     ++	test_must_fail git checkout --track=fetch -b bogus fetch_upstream/does_not_exist &&
      +	test_must_fail git rev-parse --verify refs/heads/bogus
      +'
      +
     -+test_expect_success 'checkout.fetch=true enables fetching without --fetch' '
     ++test_expect_success 'checkout --track=fetch,inherit fetches and inherits' '
      +	git checkout main &&
     -+	git -C fetch_upstream checkout -b fetch_cfg &&
     -+	test_commit -C fetch_upstream u_cfg &&
     -+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_cfg &&
     -+	git -c checkout.fetch=true checkout -b local_cfg fetch_upstream/fetch_cfg &&
     -+	test_cmp_rev refs/remotes/fetch_upstream/fetch_cfg HEAD
     -+'
     -+
     -+test_expect_success '--no-fetch overrides checkout.fetch=true' '
     ++	git -C fetch_upstream checkout -b fetch_inherit &&
     ++	test_commit -C fetch_upstream u_inherit &&
     ++	git fetch fetch_upstream fetch_inherit &&
     ++	git checkout -b base_inherit fetch_upstream/fetch_inherit &&
     ++	test_commit -C fetch_upstream u_inherit2 &&
      +	git checkout main &&
     -+	git -C fetch_upstream checkout -b fetch_nofetch &&
     -+	test_commit -C fetch_upstream u_nofetch &&
     -+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_nofetch &&
     -+	test_must_fail git -c checkout.fetch=true checkout --no-fetch \
     -+		-b local_nofetch fetch_upstream/fetch_nofetch &&
     -+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_nofetch &&
     -+	test_must_fail git rev-parse --verify refs/heads/local_nofetch
     ++	git checkout --track=fetch,inherit -b local_inherit base_inherit &&
     ++	test_cmp_rev refs/remotes/fetch_upstream/fetch_inherit HEAD &&
     ++	test_cmp_config fetch_upstream branch.local_inherit.remote &&
     ++	test_cmp_config refs/heads/fetch_inherit branch.local_inherit.merge
      +'
      +
     -+test_expect_success '--no-fetch overrides earlier --fetch on command line' '
     ++test_expect_success 'checkout --track=bogus reports an error' '
      +	git checkout main &&
     -+	git -C fetch_upstream checkout -b fetch_override &&
     -+	test_commit -C fetch_upstream u_override &&
     -+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_override &&
     -+	test_must_fail git checkout --fetch --no-fetch \
     -+		-b local_override fetch_upstream/fetch_override &&
     -+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_override &&
     -+	test_must_fail git rev-parse --verify refs/heads/local_override
     ++	test_must_fail git checkout --track=bogus -b bogus_branch fetch_upstream/fetch_new 2>err &&
     ++	test_grep "expects" err
      +'
      +
     -+test_expect_success 'switch --fetch -c picks up branch created upstream after clone' '
     ++test_expect_success 'switch --track=fetch -c picks up branch created upstream after clone' '
      +	git checkout main &&
      +	git -C fetch_upstream checkout -b fetch_switch &&
      +	test_commit -C fetch_upstream u_switch &&
      +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
     -+	git switch --fetch -c local_switch fetch_upstream/fetch_switch &&
     ++	git switch --track=fetch -c local_switch fetch_upstream/fetch_switch &&
      +	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
      +'
      +
       test_done
     -
     - ## t/t9902-completion.sh ##
     -@@ t/t9902-completion.sh: test_expect_success 'double dash "git checkout"' '
     - 	--ignore-other-worktrees Z
     - 	--recurse-submodules Z
     - 	--auto-advance Z
     -+	--fetch Z
     - 	--progress Z
     - 	--guess Z
     - 	--no-guess Z


 Documentation/git-checkout.adoc | 10 +++-
 Documentation/git-switch.adoc   | 10 +++-
 builtin/checkout.c              | 85 +++++++++++++++++++++++++++++++--
 t/t7201-co.sh                   | 81 +++++++++++++++++++++++++++++++
 4 files changed, 179 insertions(+), 7 deletions(-)

diff --git a/Documentation/git-checkout.adoc b/Documentation/git-checkout.adoc
index 43ccf47cf6..3b8292612d 100644
--- a/Documentation/git-checkout.adoc
+++ b/Documentation/git-checkout.adoc
@@ -158,11 +158,19 @@ of it").
 	resets _<branch>_ to the start point instead of failing.
 
 `-t`::
-`--track[=(direct|inherit)]`::
+`--track[=(direct|inherit|fetch)[,...]]`::
 	When creating a new branch, set up "upstream" configuration. See
 	`--track` in linkgit:git-branch[1] for details. As a convenience,
 	--track without -b implies branch creation.
 +
+The argument is a comma-separated list. `direct` (the default) and
+`inherit` select the tracking mode. Adding `fetch` requests that the
+remote be fetched before _<start-point>_ is resolved, so the new branch
+starts from a fresh tip: when _<start-point>_ is in
+_<remote>/<branch>_ form, only that branch is updated; when it is a
+bare remote name (e.g. `origin`), the whole remote is fetched. If the
+fetch fails, the checkout is aborted.
++
 If no `-b` option is given, the name of the new branch will be
 derived from the remote-tracking branch, by looking at the local part of
 the refspec configured for the corresponding remote, and then stripping
diff --git a/Documentation/git-switch.adoc b/Documentation/git-switch.adoc
index 87707e9265..35a03e8a52 100644
--- a/Documentation/git-switch.adoc
+++ b/Documentation/git-switch.adoc
@@ -154,11 +154,19 @@ should result in deletion of the path).
 	attached to a terminal, regardless of `--quiet`.
 
 `-t`::
-`--track[ (direct|inherit)]`::
+`--track[=(direct|inherit|fetch)[,...]]`::
 	When creating a new branch, set up "upstream" configuration.
 	`-c` is implied. See `--track` in linkgit:git-branch[1] for
 	details.
 +
+The argument is a comma-separated list. `direct` (the default) and
+`inherit` select the tracking mode. Adding `fetch` requests that the
+remote be fetched before _<start-point>_ is resolved, so the new branch
+starts from a fresh tip: when _<start-point>_ is in
+_<remote>/<branch>_ form, only that branch is updated; when it is a
+bare remote name (e.g. `origin`), the whole remote is fetched. If the
+fetch fails, the switch is aborted.
++
 If no `-c` option is given, the name of the new branch will be derived
 from the remote-tracking branch, by looking at the local part of the
 refspec configured for the corresponding remote, and then stripping
diff --git a/builtin/checkout.c b/builtin/checkout.c
index e031e61886..de4d7c00c7 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -30,7 +30,9 @@
 #include "repo-settings.h"
 #include "resolve-undo.h"
 #include "revision.h"
+#include "run-command.h"
 #include "setup.h"
+#include "strvec.h"
 #include "submodule.h"
 #include "symlinks.h"
 #include "trace2.h"
@@ -61,6 +63,7 @@ struct checkout_opts {
 	int count_checkout_paths;
 	int overlay_mode;
 	int dwim_new_local_branch;
+	int fetch;
 	int discard_changes;
 	int accept_ref;
 	int accept_pathspec;
@@ -112,6 +115,74 @@ struct branch_info {
 	char *checkout;
 };
 
+static void fetch_remote_for_start_point(const char *arg)
+{
+	const char *slash;
+	char *remote_name;
+	struct remote *remote;
+	struct child_process cmd = CHILD_PROCESS_INIT;
+
+	if (!arg || !*arg)
+		return;
+
+	slash = strchr(arg, '/');
+	if (slash == arg)
+		return;
+	remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
+
+	remote = remote_get(remote_name);
+	if (!remote || !remote_is_configured(remote, 1)) {
+		free(remote_name);
+		return;
+	}
+
+	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
+	if (slash && slash[1])
+		strvec_push(&cmd.args, slash + 1);
+	cmd.git_cmd = 1;
+	free(remote_name);
+	if (run_command(&cmd))
+		die(_("failed to fetch start-point '%s'"), arg);
+}
+
+static int parse_opt_checkout_track(const struct option *opt,
+				    const char *arg, int unset)
+{
+	struct checkout_opts *opts = opt->value;
+	struct string_list tokens = STRING_LIST_INIT_DUP;
+	struct string_list_item *item;
+	int ret = 0;
+
+	if (unset) {
+		opts->track = BRANCH_TRACK_NEVER;
+		opts->fetch = 0;
+		return 0;
+	}
+
+	opts->track = BRANCH_TRACK_EXPLICIT;
+	if (!arg)
+		return 0;
+
+	string_list_split(&tokens, arg, ",", -1);
+	for_each_string_list_item(item, &tokens) {
+		if (!strcmp(item->string, "fetch")) {
+			opts->fetch = 1;
+		} else if (!strcmp(item->string, "direct")) {
+			opts->track = BRANCH_TRACK_EXPLICIT;
+		} else if (!strcmp(item->string, "inherit")) {
+			opts->track = BRANCH_TRACK_INHERIT;
+		} else {
+			ret = error(_("option `%s' expects \"%s\", \"%s\", "
+				      "or \"%s\""),
+				    "--track", "direct", "inherit", "fetch");
+			break;
+		}
+	}
+
+	string_list_clear(&tokens, 0);
+	return ret;
+}
+
 static void branch_info_release(struct branch_info *info)
 {
 	free(info->name);
@@ -1237,7 +1308,6 @@ static int git_checkout_config(const char *var, const char *value,
 		opts->dwim_new_local_branch = git_config_bool(var, value);
 		return 0;
 	}
-
 	if (starts_with(var, "submodule."))
 		return git_default_submodule_config(var, value, NULL);
 
@@ -1734,10 +1804,10 @@ static struct option *add_common_switch_branch_options(
 {
 	struct option options[] = {
 		OPT_BOOL('d', "detach", &opts->force_detach, N_("detach HEAD at named commit")),
-		OPT_CALLBACK_F('t', "track",  &opts->track, "(direct|inherit)",
+		OPT_CALLBACK_F('t', "track",  opts, "(direct|inherit|fetch)[,...]",
 			N_("set branch tracking configuration"),
 			PARSE_OPT_OPTARG,
-			parse_opt_tracking_mode),
+			parse_opt_checkout_track),
 		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
 			   PARSE_OPT_NOCOMPLETE),
 		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unborn branch")),
@@ -1942,8 +2012,13 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 			opts->dwim_new_local_branch &&
 			opts->track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts->new_branch;
-		int n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
-					     &new_branch_info, opts, &rev);
+		int n;
+
+		if (opts->fetch)
+			fetch_remote_for_start_point(argv[0]);
+
+		n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
+					 &new_branch_info, opts, &rev);
 		argv += n;
 		argc -= n;
 	} else if (!opts->accept_ref && opts->from_treeish) {
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 9bcf7c0b40..39236dca12 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -801,4 +801,85 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
 	test_cmp_config "" --default "" branch.main2.merge
 '
 
+test_expect_success 'setup upstream for --track=fetch tests' '
+	git checkout main &&
+	git init fetch_upstream &&
+	test_commit -C fetch_upstream u_main &&
+	git remote add fetch_upstream fetch_upstream &&
+	git fetch fetch_upstream &&
+	git -C fetch_upstream checkout -b fetch_new &&
+	test_commit -C fetch_upstream u_new
+'
+
+test_expect_success 'checkout --track=fetch -b picks up branch created upstream after clone' '
+	git checkout main &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
+	git checkout --track=fetch -b local_new fetch_upstream/fetch_new &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD &&
+	test_cmp_config fetch_upstream branch.local_new.remote &&
+	test_cmp_config refs/heads/fetch_new branch.local_new.merge
+'
+
+test_expect_success 'checkout --track=fetch <remote>/<branch> leaves other tracking branches untouched' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_target &&
+	test_commit -C fetch_upstream u_target_pre &&
+	git -C fetch_upstream checkout -b fetch_other &&
+	test_commit -C fetch_upstream u_other_pre &&
+	git fetch fetch_upstream &&
+	other_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_other) &&
+	git -C fetch_upstream checkout fetch_target &&
+	test_commit -C fetch_upstream u_target_post &&
+	git -C fetch_upstream checkout fetch_other &&
+	test_commit -C fetch_upstream u_other_post &&
+	git checkout --track=fetch -b local_target fetch_upstream/fetch_target &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_target HEAD &&
+	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before"
+'
+
+test_expect_success 'checkout --track=fetch with bare remote name fetches the remote' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_new2 &&
+	test_commit -C fetch_upstream u_new2 &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2 &&
+	git checkout --track=fetch -b local_from_remote fetch_upstream &&
+	git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2
+'
+
+test_expect_success 'checkout --track=fetch aborts and does not create branch on fetch failure' '
+	git checkout main &&
+	test_might_fail git branch -D bogus &&
+	test_must_fail git checkout --track=fetch -b bogus fetch_upstream/does_not_exist &&
+	test_must_fail git rev-parse --verify refs/heads/bogus
+'
+
+test_expect_success 'checkout --track=fetch,inherit fetches and inherits' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_inherit &&
+	test_commit -C fetch_upstream u_inherit &&
+	git fetch fetch_upstream fetch_inherit &&
+	git checkout -b base_inherit fetch_upstream/fetch_inherit &&
+	test_commit -C fetch_upstream u_inherit2 &&
+	git checkout main &&
+	git checkout --track=fetch,inherit -b local_inherit base_inherit &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_inherit HEAD &&
+	test_cmp_config fetch_upstream branch.local_inherit.remote &&
+	test_cmp_config refs/heads/fetch_inherit branch.local_inherit.merge
+'
+
+test_expect_success 'checkout --track=bogus reports an error' '
+	git checkout main &&
+	test_must_fail git checkout --track=bogus -b bogus_branch fetch_upstream/fetch_new 2>err &&
+	test_grep "expects" err
+'
+
+test_expect_success 'switch --track=fetch -c picks up branch created upstream after clone' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_switch &&
+	test_commit -C fetch_upstream u_switch &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
+	git switch --track=fetch -c local_switch fetch_upstream/fetch_switch &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
+'
+
 test_done

base-commit: 94f057755b7941b321fd11fec1b2e3ca5313a4e0
-- 
gitgitgadget

Re: [PATCH v5] checkout: extend --track with a "fetch" mode to refresh start-point

[Junio C Hamano]

"Harald Nordgren via GitGitGadget" <gitgitgadget@gmail.com> writes:

> From: Harald Nordgren <haraldnordgren@gmail.com>
>
> A common workflow is:
>
>     git fetch origin
>     git checkout -b new_branch --track origin/some-branch
>
> The first command exists so the second sees an up-to-date view of the
> remote. If it is forgotten, origin/some-branch points at a stale
> commit and the new local branch is created from the wrong start
> point.

As I pointed out multiple times, I prefer not to see this called
"wrong".  Even if you did not "forget", somebody may be pushing
after you fetched and you may end up forking from a "stale" commit.
So not fetching is not inherently "wrong", simply because that is
how real world works.  Multiple people working in a distributed
environment does not give you absolute garantee that you will be "up
to date", ever, which makes it wrong to call anything that is not
"up to date" a "wrong starting point".

> This only matters when the user is setting up tracking and
> expects the new branch to start at the freshest tip; for a one-off
> checkout of an arbitrary commit there is no reason to "freshen" the
> start-point.

I do not think "arbitrary" fits in this workflow description.

If anything, "I'd take anything that the remote repository happens
to have at the tip, even without having a chance to sanity checke if
that is a good starting point" is more appropriate workflow to be
described with a word "arbitrary commit".

If you are checking out without forking from there, you'd more
likely be checking out the "latest" you have fetched from the other
side, often knowing exactly what it is after checking it with "git
show origin/$topic".

> Tie the new behavior to --track for that reason:

Notice that the reader hasn't heard what "the new behaviour" is up
to this point yet?

How about rewriting everything up to and including this "Tie the new
..." line perhaps like so:

    If you want to fork your topic branch from the very latest of
    the tip of a branch your remote has, you would do:

	git fetch origin some-branch
	git checkout -b new_branch --track origin/some-branch

    Extend the "--track" option of "git checkout" and allow users to
    write

	git checkout --track=fetch -b new_branch origin/some_branch

    to (1) fetch 'some-branch' from the remote 'origin', updating
    the remote-tracking branch 'origin/some-branch', (2) arrange
    subsequent 'git pull' on 'new_branch' to interact with
    'origin/some_branch' and (3) fork 'new_branch' from it.
   
    In the value of the '--track' option, 'fetch' can be combined
    with ...

[PATCH] checkout: add --autostash option for branch switching

[Harald Nordgren]

> How about rewriting everything up to and including this "Tie the new
> ..." line perhaps like so:

Done!


Harald

[PATCH v6] checkout: extend --track with a "fetch" mode to refresh start-point

[Harald Nordgren via GitGitGadget]

From: Harald Nordgren <haraldnordgren@gmail.com>

If you want to fork your topic branch from the very latest of the
tip of a branch your remote has, you would do:

    git fetch origin some-branch
    git checkout -b new_branch --track origin/some-branch

Extend the "--track" option of "git checkout" and allow users to
write

    git checkout -b new_branch --track=fetch origin/some-branch

to (1) fetch 'some-branch' from the remote 'origin', updating the
remote-tracking branch 'origin/some-branch', (2) arrange subsequent
'git pull' on 'new_branch' to interact with 'origin/some-branch' and
(3) fork 'new_branch' from it.

In the value of the '--track' option, 'fetch' can be combined with
the existing 'direct' (default) and 'inherit' modes via a
comma-separated list. Examples:

    git checkout -b new_branch --track=fetch,inherit some_local_branch
    git switch -c new_branch --track=fetch origin/some-branch

When "fetch" is requested and <start-point> is in <remote>/<branch>
form, run "git fetch <remote> <branch>" before resolving the ref, so
that other remote-tracking branches are left untouched. If
<start-point> is a bare remote name like "origin" (which resolves to
that remote's default branch), "git fetch <remote>" is run instead,
since the target branch is not known up front. Abort the checkout if
the fetch fails.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
    checkout: add --fetch to fetch remote before resolving start-point
    
    Commit message only, no code/doc/test changes. Restructured the opening
    around the user-visible workflow before introducing '--track=fetch',
    reordered all example invocations to ' -b/-c --track[=...] ', dropped
    the "wrong/stale start-point" and "arbitrary commit" framings, and
    trimmed the over-explanation of the narrowed fetch.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2281%2FHaraldNordgren%2Fcheckout-fetch-start-point-v6
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2281/HaraldNordgren/checkout-fetch-start-point-v6
Pull-Request: https://github.com/git/git/pull/2281

Range-diff vs v5:

 1:  8ebc2f94b9 ! 1:  1b42c648b9 checkout: extend --track with a "fetch" mode to refresh start-point
     @@ Metadata
       ## Commit message ##
          checkout: extend --track with a "fetch" mode to refresh start-point
      
     -    A common workflow is:
     +    If you want to fork your topic branch from the very latest of the
     +    tip of a branch your remote has, you would do:
      
     -        git fetch origin
     +        git fetch origin some-branch
              git checkout -b new_branch --track origin/some-branch
      
     -    The first command exists so the second sees an up-to-date view of the
     -    remote. If it is forgotten, origin/some-branch points at a stale
     -    commit and the new local branch is created from the wrong start
     -    point. This only matters when the user is setting up tracking and
     -    expects the new branch to start at the freshest tip; for a one-off
     -    checkout of an arbitrary commit there is no reason to "freshen" the
     -    start-point.
     +    Extend the "--track" option of "git checkout" and allow users to
     +    write
      
     -    Tie the new behavior to --track for that reason: extend its argument
     -    to take a comma-separated list, where "fetch" can be combined with the
     -    existing "direct" (default) and "inherit" modes. Examples:
     +        git checkout -b new_branch --track=fetch origin/some-branch
      
     -        git checkout --track=fetch -b new_branch origin/some-branch
     -        git checkout --track=fetch,inherit -b new_branch some_local_branch
     -        git switch --track=fetch -c new_branch origin/some-branch
     +    to (1) fetch 'some-branch' from the remote 'origin', updating the
     +    remote-tracking branch 'origin/some-branch', (2) arrange subsequent
     +    'git pull' on 'new_branch' to interact with 'origin/some-branch' and
     +    (3) fork 'new_branch' from it.
     +
     +    In the value of the '--track' option, 'fetch' can be combined with
     +    the existing 'direct' (default) and 'inherit' modes via a
     +    comma-separated list. Examples:
     +
     +        git checkout -b new_branch --track=fetch,inherit some_local_branch
     +        git switch -c new_branch --track=fetch origin/some-branch
      
          When "fetch" is requested and <start-point> is in <remote>/<branch>
     -    form, run "git fetch <remote> <branch>" before resolving the ref. This
     -    narrows the fetch to the requested branch so that other
     -    remote-tracking branches are left untouched -- many tools rely on the
     -    stability of remote-tracking refs between explicit fetches. If
     +    form, run "git fetch <remote> <branch>" before resolving the ref, so
     +    that other remote-tracking branches are left untouched. If
          <start-point> is a bare remote name like "origin" (which resolves to
          that remote's default branch), "git fetch <remote>" is run instead,
          since the target branch is not known up front. Abort the checkout if


 Documentation/git-checkout.adoc | 10 +++-
 Documentation/git-switch.adoc   | 10 +++-
 builtin/checkout.c              | 85 +++++++++++++++++++++++++++++++--
 t/t7201-co.sh                   | 81 +++++++++++++++++++++++++++++++
 4 files changed, 179 insertions(+), 7 deletions(-)

diff --git a/Documentation/git-checkout.adoc b/Documentation/git-checkout.adoc
index 43ccf47cf6..3b8292612d 100644
--- a/Documentation/git-checkout.adoc
+++ b/Documentation/git-checkout.adoc
@@ -158,11 +158,19 @@ of it").
 	resets _<branch>_ to the start point instead of failing.
 
 `-t`::
-`--track[=(direct|inherit)]`::
+`--track[=(direct|inherit|fetch)[,...]]`::
 	When creating a new branch, set up "upstream" configuration. See
 	`--track` in linkgit:git-branch[1] for details. As a convenience,
 	--track without -b implies branch creation.
 +
+The argument is a comma-separated list. `direct` (the default) and
+`inherit` select the tracking mode. Adding `fetch` requests that the
+remote be fetched before _<start-point>_ is resolved, so the new branch
+starts from a fresh tip: when _<start-point>_ is in
+_<remote>/<branch>_ form, only that branch is updated; when it is a
+bare remote name (e.g. `origin`), the whole remote is fetched. If the
+fetch fails, the checkout is aborted.
++
 If no `-b` option is given, the name of the new branch will be
 derived from the remote-tracking branch, by looking at the local part of
 the refspec configured for the corresponding remote, and then stripping
diff --git a/Documentation/git-switch.adoc b/Documentation/git-switch.adoc
index 87707e9265..35a03e8a52 100644
--- a/Documentation/git-switch.adoc
+++ b/Documentation/git-switch.adoc
@@ -154,11 +154,19 @@ should result in deletion of the path).
 	attached to a terminal, regardless of `--quiet`.
 
 `-t`::
-`--track[ (direct|inherit)]`::
+`--track[=(direct|inherit|fetch)[,...]]`::
 	When creating a new branch, set up "upstream" configuration.
 	`-c` is implied. See `--track` in linkgit:git-branch[1] for
 	details.
 +
+The argument is a comma-separated list. `direct` (the default) and
+`inherit` select the tracking mode. Adding `fetch` requests that the
+remote be fetched before _<start-point>_ is resolved, so the new branch
+starts from a fresh tip: when _<start-point>_ is in
+_<remote>/<branch>_ form, only that branch is updated; when it is a
+bare remote name (e.g. `origin`), the whole remote is fetched. If the
+fetch fails, the switch is aborted.
++
 If no `-c` option is given, the name of the new branch will be derived
 from the remote-tracking branch, by looking at the local part of the
 refspec configured for the corresponding remote, and then stripping
diff --git a/builtin/checkout.c b/builtin/checkout.c
index e031e61886..de4d7c00c7 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -30,7 +30,9 @@
 #include "repo-settings.h"
 #include "resolve-undo.h"
 #include "revision.h"
+#include "run-command.h"
 #include "setup.h"
+#include "strvec.h"
 #include "submodule.h"
 #include "symlinks.h"
 #include "trace2.h"
@@ -61,6 +63,7 @@ struct checkout_opts {
 	int count_checkout_paths;
 	int overlay_mode;
 	int dwim_new_local_branch;
+	int fetch;
 	int discard_changes;
 	int accept_ref;
 	int accept_pathspec;
@@ -112,6 +115,74 @@ struct branch_info {
 	char *checkout;
 };
 
+static void fetch_remote_for_start_point(const char *arg)
+{
+	const char *slash;
+	char *remote_name;
+	struct remote *remote;
+	struct child_process cmd = CHILD_PROCESS_INIT;
+
+	if (!arg || !*arg)
+		return;
+
+	slash = strchr(arg, '/');
+	if (slash == arg)
+		return;
+	remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
+
+	remote = remote_get(remote_name);
+	if (!remote || !remote_is_configured(remote, 1)) {
+		free(remote_name);
+		return;
+	}
+
+	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
+	if (slash && slash[1])
+		strvec_push(&cmd.args, slash + 1);
+	cmd.git_cmd = 1;
+	free(remote_name);
+	if (run_command(&cmd))
+		die(_("failed to fetch start-point '%s'"), arg);
+}
+
+static int parse_opt_checkout_track(const struct option *opt,
+				    const char *arg, int unset)
+{
+	struct checkout_opts *opts = opt->value;
+	struct string_list tokens = STRING_LIST_INIT_DUP;
+	struct string_list_item *item;
+	int ret = 0;
+
+	if (unset) {
+		opts->track = BRANCH_TRACK_NEVER;
+		opts->fetch = 0;
+		return 0;
+	}
+
+	opts->track = BRANCH_TRACK_EXPLICIT;
+	if (!arg)
+		return 0;
+
+	string_list_split(&tokens, arg, ",", -1);
+	for_each_string_list_item(item, &tokens) {
+		if (!strcmp(item->string, "fetch")) {
+			opts->fetch = 1;
+		} else if (!strcmp(item->string, "direct")) {
+			opts->track = BRANCH_TRACK_EXPLICIT;
+		} else if (!strcmp(item->string, "inherit")) {
+			opts->track = BRANCH_TRACK_INHERIT;
+		} else {
+			ret = error(_("option `%s' expects \"%s\", \"%s\", "
+				      "or \"%s\""),
+				    "--track", "direct", "inherit", "fetch");
+			break;
+		}
+	}
+
+	string_list_clear(&tokens, 0);
+	return ret;
+}
+
 static void branch_info_release(struct branch_info *info)
 {
 	free(info->name);
@@ -1237,7 +1308,6 @@ static int git_checkout_config(const char *var, const char *value,
 		opts->dwim_new_local_branch = git_config_bool(var, value);
 		return 0;
 	}
-
 	if (starts_with(var, "submodule."))
 		return git_default_submodule_config(var, value, NULL);
 
@@ -1734,10 +1804,10 @@ static struct option *add_common_switch_branch_options(
 {
 	struct option options[] = {
 		OPT_BOOL('d', "detach", &opts->force_detach, N_("detach HEAD at named commit")),
-		OPT_CALLBACK_F('t', "track",  &opts->track, "(direct|inherit)",
+		OPT_CALLBACK_F('t', "track",  opts, "(direct|inherit|fetch)[,...]",
 			N_("set branch tracking configuration"),
 			PARSE_OPT_OPTARG,
-			parse_opt_tracking_mode),
+			parse_opt_checkout_track),
 		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
 			   PARSE_OPT_NOCOMPLETE),
 		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unborn branch")),
@@ -1942,8 +2012,13 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 			opts->dwim_new_local_branch &&
 			opts->track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts->new_branch;
-		int n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
-					     &new_branch_info, opts, &rev);
+		int n;
+
+		if (opts->fetch)
+			fetch_remote_for_start_point(argv[0]);
+
+		n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
+					 &new_branch_info, opts, &rev);
 		argv += n;
 		argc -= n;
 	} else if (!opts->accept_ref && opts->from_treeish) {
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 9bcf7c0b40..39236dca12 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -801,4 +801,85 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
 	test_cmp_config "" --default "" branch.main2.merge
 '
 
+test_expect_success 'setup upstream for --track=fetch tests' '
+	git checkout main &&
+	git init fetch_upstream &&
+	test_commit -C fetch_upstream u_main &&
+	git remote add fetch_upstream fetch_upstream &&
+	git fetch fetch_upstream &&
+	git -C fetch_upstream checkout -b fetch_new &&
+	test_commit -C fetch_upstream u_new
+'
+
+test_expect_success 'checkout --track=fetch -b picks up branch created upstream after clone' '
+	git checkout main &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
+	git checkout --track=fetch -b local_new fetch_upstream/fetch_new &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD &&
+	test_cmp_config fetch_upstream branch.local_new.remote &&
+	test_cmp_config refs/heads/fetch_new branch.local_new.merge
+'
+
+test_expect_success 'checkout --track=fetch <remote>/<branch> leaves other tracking branches untouched' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_target &&
+	test_commit -C fetch_upstream u_target_pre &&
+	git -C fetch_upstream checkout -b fetch_other &&
+	test_commit -C fetch_upstream u_other_pre &&
+	git fetch fetch_upstream &&
+	other_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_other) &&
+	git -C fetch_upstream checkout fetch_target &&
+	test_commit -C fetch_upstream u_target_post &&
+	git -C fetch_upstream checkout fetch_other &&
+	test_commit -C fetch_upstream u_other_post &&
+	git checkout --track=fetch -b local_target fetch_upstream/fetch_target &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_target HEAD &&
+	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before"
+'
+
+test_expect_success 'checkout --track=fetch with bare remote name fetches the remote' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_new2 &&
+	test_commit -C fetch_upstream u_new2 &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2 &&
+	git checkout --track=fetch -b local_from_remote fetch_upstream &&
+	git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2
+'
+
+test_expect_success 'checkout --track=fetch aborts and does not create branch on fetch failure' '
+	git checkout main &&
+	test_might_fail git branch -D bogus &&
+	test_must_fail git checkout --track=fetch -b bogus fetch_upstream/does_not_exist &&
+	test_must_fail git rev-parse --verify refs/heads/bogus
+'
+
+test_expect_success 'checkout --track=fetch,inherit fetches and inherits' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_inherit &&
+	test_commit -C fetch_upstream u_inherit &&
+	git fetch fetch_upstream fetch_inherit &&
+	git checkout -b base_inherit fetch_upstream/fetch_inherit &&
+	test_commit -C fetch_upstream u_inherit2 &&
+	git checkout main &&
+	git checkout --track=fetch,inherit -b local_inherit base_inherit &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_inherit HEAD &&
+	test_cmp_config fetch_upstream branch.local_inherit.remote &&
+	test_cmp_config refs/heads/fetch_inherit branch.local_inherit.merge
+'
+
+test_expect_success 'checkout --track=bogus reports an error' '
+	git checkout main &&
+	test_must_fail git checkout --track=bogus -b bogus_branch fetch_upstream/fetch_new 2>err &&
+	test_grep "expects" err
+'
+
+test_expect_success 'switch --track=fetch -c picks up branch created upstream after clone' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_switch &&
+	test_commit -C fetch_upstream u_switch &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
+	git switch --track=fetch -c local_switch fetch_upstream/fetch_switch &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
+'
+
 test_done

base-commit: 94f057755b7941b321fd11fec1b2e3ca5313a4e0
-- 
gitgitgadget

[PATCH v6] checkout: extend --track with a "fetch" mode to refresh start-point

[Harald Nordgren]

Is this ready to move to next?


Harald

Re: [PATCH v6] checkout: extend --track with a "fetch" mode to refresh start-point

[Phillip Wood]

Hi Harald

On 07/05/2026 21:12, Harald Nordgren wrote:
> Is this ready to move to next?

I'm not particularly enthusiastic one way or the other about adding 
this, but so long as we only try to fetch when the user explicitly asks 
for it I don't particularly object. However having had a quick scan of 
the implementation I have a few comments

* "--track=inherit,direct" is nonsense and should be rejected

* currently "--track" has "last one wins" behavior so
   "--track=inherit --track=direct" behaves like "--track=direct". We
   should probably keep that so that "--track=fetch --track=direct"
   behaves like "--track=direct", not "--track=fetch,direct"

* if "git fetch" fails and the remote tracking ref already exists then
   we should print a warning and carry on rather than dying which is more
   convenient if the user or remote server are offline.

* "git checkout --track=fetch origin/branch" should respect
   remote.origin.fetch so that we fetch the ref that we're going to
   checkout. I wonder if we can share this logic with the code that
   sets the upstream branch.

* "git checkout --track=fetch origin" should only fetch the remote
   ref that we're going to checkout, not all the refs from origin. i.e.
   it should read origin/HEAD to work out what to fetch.

Thanks

Phillip

[PATCH] checkout: add --fetch to fetch remote before resolving start-point

[Harald Nordgren]

> * "--track=inherit,direct" is nonsense and should be rejected
> 
> * currently "--track" has "last one wins" behavior so
>   "--track=inherit --track=direct" behaves like "--track=direct". We
>   should probably keep that so that "--track=fetch --track=direct"
>   behaves like "--track=direct", not "--track=fetch,direct"
> 
> * if "git fetch" fails and the remote tracking ref already exists then
>   we should print a warning and carry on rather than dying which is more
>   convenient if the user or remote server are offline.
> 
> * "git checkout --track=fetch origin/branch" should respect
>   remote.origin.fetch so that we fetch the ref that we're going to
>   checkout. I wonder if we can share this logic with the code that
>   sets the upstream branch.
> 
> * "git checkout --track=fetch origin" should only fetch the remote
>   ref that we're going to checkout, not all the refs from origin. i.e.
>   it should read origin/HEAD to work out what to fetch.

Good points!


Harald

[PATCH v7] checkout: extend --track with a "fetch" mode to refresh start-point

[Harald Nordgren via GitGitGadget]

From: Harald Nordgren <haraldnordgren@gmail.com>

If you want to fork your topic branch from the very latest of the
tip of a branch your remote has, you would do:

    git fetch origin some-branch
    git checkout -b new_branch --track origin/some-branch

Extend the "--track" option of "git checkout" and allow users to
write

    git checkout -b new_branch --track=fetch origin/some-branch

to (1) fetch 'some-branch' from the remote 'origin', updating the
remote-tracking branch 'origin/some-branch', (2) arrange subsequent
'git pull' on 'new_branch' to interact with 'origin/some-branch' and
(3) fork 'new_branch' from it.

In the value of the '--track' option, 'fetch' can be combined with
the existing 'direct' (default) and 'inherit' modes via a
comma-separated list. Examples:

    git checkout -b new_branch --track=fetch,inherit some_local_branch
    git switch -c new_branch --track=fetch origin/some-branch

When "fetch" is requested and <start-point> is in <remote>/<branch>
form, run "git fetch <remote> <branch>" before resolving the ref, so
that other remote-tracking branches are left untouched. If
<start-point> is a bare remote name like "origin" (which resolves to
that remote's default branch), "git fetch <remote>" is run instead,
since the target branch is not known up front. Abort the checkout if
the fetch fails.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
    checkout: add --fetch to fetch remote before resolving start-point
    
     * Reject --track=inherit,direct as mutually exclusive modes.
     * Make repeated --track= last-one-wins: --track=fetch --track=direct
       behaves like --track=direct.
     * On fetch failure, warn and proceed from the existing remote-tracking
       ref instead of aborting (friendlier when offline); only abort when
       there is no existing ref.
     * For --track=fetch <remote>/<branch>, resolve the source ref through
       the configured remote.<name>.fetch refspec so custom refspecs fetch
       the correct ref.
     * For --track=fetch <remote>, read <remote>/HEAD and fetch only that
       branch instead of the whole remote.
     * Tests and docs updated accordingly.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2281%2FHaraldNordgren%2Fcheckout-fetch-start-point-v7
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2281/HaraldNordgren/checkout-fetch-start-point-v7
Pull-Request: https://github.com/git/git/pull/2281

Range-diff vs v6:

 1:  1b42c648b9 ! 1:  de375d55f1 checkout: extend --track with a "fetch" mode to refresh start-point
     @@ Documentation/git-checkout.adoc: of it").
       	--track without -b implies branch creation.
       +
      +The argument is a comma-separated list. `direct` (the default) and
     -+`inherit` select the tracking mode. Adding `fetch` requests that the
     -+remote be fetched before _<start-point>_ is resolved, so the new branch
     -+starts from a fresh tip: when _<start-point>_ is in
     -+_<remote>/<branch>_ form, only that branch is updated; when it is a
     -+bare remote name (e.g. `origin`), the whole remote is fetched. If the
     -+fetch fails, the checkout is aborted.
     ++`inherit` select the tracking mode and are mutually exclusive. Adding
     ++`fetch` requests that the remote be fetched before _<start-point>_ is
     ++resolved, so the new branch starts from a fresh tip: when
     ++_<start-point>_ is in _<remote>/<branch>_ form, only that branch is
     ++updated; when _<start-point>_ is a bare remote name (e.g. `origin`),
     ++only the remote's default branch is updated. If the fetch fails and the
     ++corresponding remote-tracking ref already exists, a warning is printed
     ++and the checkout proceeds from the existing tip; otherwise the checkout
     ++is aborted.
      ++
       If no `-b` option is given, the name of the new branch will be
       derived from the remote-tracking branch, by looking at the local part of
     @@ Documentation/git-switch.adoc: should result in deletion of the path).
       	details.
       +
      +The argument is a comma-separated list. `direct` (the default) and
     -+`inherit` select the tracking mode. Adding `fetch` requests that the
     -+remote be fetched before _<start-point>_ is resolved, so the new branch
     -+starts from a fresh tip: when _<start-point>_ is in
     -+_<remote>/<branch>_ form, only that branch is updated; when it is a
     -+bare remote name (e.g. `origin`), the whole remote is fetched. If the
     -+fetch fails, the switch is aborted.
     ++`inherit` select the tracking mode and are mutually exclusive. Adding
     ++`fetch` requests that the remote be fetched before _<start-point>_ is
     ++resolved, so the new branch starts from a fresh tip: when
     ++_<start-point>_ is in _<remote>/<branch>_ form, only that branch is
     ++updated; when _<start-point>_ is a bare remote name (e.g. `origin`),
     ++only the remote's default branch is updated. If the fetch fails and the
     ++corresponding remote-tracking ref already exists, a warning is printed
     ++and the switch proceeds from the existing tip; otherwise the switch is
     ++aborted.
      ++
       If no `-c` option is given, the name of the new branch will be derived
       from the remote-tracking branch, by looking at the local part of the
     @@ Documentation/git-switch.adoc: should result in deletion of the path).
      
       ## builtin/checkout.c ##
      @@
     + #include "preload-index.h"
     + #include "read-cache.h"
     + #include "refs.h"
     ++#include "refspec.h"
     + #include "remote.h"
       #include "repo-settings.h"
       #include "resolve-undo.h"
       #include "revision.h"
     @@ builtin/checkout.c: struct branch_info {
       	char *checkout;
       };
       
     -+static void fetch_remote_for_start_point(const char *arg)
     ++static int resolve_fetch_target(const char *arg, char **remote_out,
     ++				char **src_ref_out)
      +{
      +	const char *slash;
      +	char *remote_name;
      +	struct remote *remote;
     -+	struct child_process cmd = CHILD_PROCESS_INIT;
     ++	struct refspec_item query = { 0 };
     ++	struct strbuf dst = STRBUF_INIT;
     ++	const char *rest;
     ++
     ++	*remote_out = NULL;
     ++	*src_ref_out = NULL;
      +
      +	if (!arg || !*arg)
     -+		return;
     ++		return -1;
      +
      +	slash = strchr(arg, '/');
      +	if (slash == arg)
     -+		return;
     ++		return -1;
      +	remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
      +
      +	remote = remote_get(remote_name);
      +	if (!remote || !remote_is_configured(remote, 1)) {
      +		free(remote_name);
     ++		return -1;
     ++	}
     ++
     ++	rest = (slash && slash[1]) ? slash + 1 : NULL;
     ++	if (!rest) {
     ++		struct object_id oid;
     ++		const char *head_target;
     ++		const char *short_target;
     ++
     ++		strbuf_addf(&dst, "refs/remotes/%s/HEAD", remote_name);
     ++		head_target = refs_resolve_ref_unsafe(get_main_ref_store(the_repository),
     ++						      dst.buf,
     ++						      RESOLVE_REF_READING |
     ++						      RESOLVE_REF_NO_RECURSE,
     ++						      &oid, NULL);
     ++		strbuf_reset(&dst);
     ++		if (head_target &&
     ++		    skip_prefix(head_target, "refs/remotes/", &short_target) &&
     ++		    skip_prefix(short_target, remote_name, &short_target) &&
     ++		    *short_target == '/')
     ++			rest = short_target + 1;
     ++	}
     ++
     ++	if (rest) {
     ++		strbuf_addf(&dst, "refs/remotes/%s/%s", remote_name, rest);
     ++		query.dst = dst.buf;
     ++		if (!remote_find_tracking(remote, &query) && query.src) {
     ++			*src_ref_out = xstrdup(query.src);
     ++			free(query.src);
     ++		} else {
     ++			*src_ref_out = xstrdup(rest);
     ++		}
     ++	}
     ++
     ++	strbuf_release(&dst);
     ++	*remote_out = remote_name;
     ++	return 0;
     ++}
     ++
     ++static void fetch_remote_for_start_point(const char *arg)
     ++{
     ++	char *remote_name = NULL;
     ++	char *src_ref = NULL;
     ++	struct child_process cmd = CHILD_PROCESS_INIT;
     ++	struct strbuf dst_ref = STRBUF_INIT;
     ++	int have_existing_ref = 0;
     ++
     ++	if (resolve_fetch_target(arg, &remote_name, &src_ref))
      +		return;
     ++
     ++	if (src_ref) {
     ++		const char *short_src = src_ref;
     ++		struct object_id oid;
     ++
     ++		skip_prefix(short_src, "refs/heads/", &short_src);
     ++		strbuf_addf(&dst_ref, "refs/remotes/%s/%s", remote_name, short_src);
     ++		if (!refs_read_ref(get_main_ref_store(the_repository),
     ++				   dst_ref.buf, &oid))
     ++			have_existing_ref = 1;
      +	}
      +
      +	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
     -+	if (slash && slash[1])
     -+		strvec_push(&cmd.args, slash + 1);
     ++	if (src_ref)
     ++		strvec_push(&cmd.args, src_ref);
      +	cmd.git_cmd = 1;
     ++	if (run_command(&cmd)) {
     ++		if (have_existing_ref)
     ++			warning(_("failed to fetch start-point '%s'; "
     ++				  "using existing '%s'"),
     ++				arg, dst_ref.buf);
     ++		else
     ++			die(_("failed to fetch start-point '%s'"), arg);
     ++	}
     ++
      +	free(remote_name);
     -+	if (run_command(&cmd))
     -+		die(_("failed to fetch start-point '%s'"), arg);
     ++	free(src_ref);
     ++	strbuf_release(&dst_ref);
      +}
      +
      +static int parse_opt_checkout_track(const struct option *opt,
     @@ builtin/checkout.c: struct branch_info {
      +	struct checkout_opts *opts = opt->value;
      +	struct string_list tokens = STRING_LIST_INIT_DUP;
      +	struct string_list_item *item;
     ++	int saw_direct = 0, saw_inherit = 0;
      +	int ret = 0;
      +
     ++	opts->fetch = 0;
     ++
      +	if (unset) {
      +		opts->track = BRANCH_TRACK_NEVER;
     -+		opts->fetch = 0;
      +		return 0;
      +	}
      +
     @@ builtin/checkout.c: struct branch_info {
      +		if (!strcmp(item->string, "fetch")) {
      +			opts->fetch = 1;
      +		} else if (!strcmp(item->string, "direct")) {
     ++			saw_direct = 1;
      +			opts->track = BRANCH_TRACK_EXPLICIT;
      +		} else if (!strcmp(item->string, "inherit")) {
     ++			saw_inherit = 1;
      +			opts->track = BRANCH_TRACK_INHERIT;
      +		} else {
      +			ret = error(_("option `%s' expects \"%s\", \"%s\", "
      +				      "or \"%s\""),
      +				    "--track", "direct", "inherit", "fetch");
     -+			break;
     ++			goto out;
      +		}
      +	}
      +
     ++	if (saw_direct && saw_inherit)
     ++		ret = error(_("option `%s' cannot combine \"%s\" and \"%s\""),
     ++			    "--track", "direct", "inherit");
     ++
     ++out:
      +	string_list_clear(&tokens, 0);
      +	return ret;
      +}
     @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh
      +	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before"
      +'
      +
     -+test_expect_success 'checkout --track=fetch with bare remote name fetches the remote' '
     ++test_expect_success 'checkout --track=fetch with bare remote name fetches only <remote>/HEAD target' '
      +	git checkout main &&
     -+	git -C fetch_upstream checkout -b fetch_new2 &&
     -+	test_commit -C fetch_upstream u_new2 &&
     -+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2 &&
     ++	git -C fetch_upstream checkout main &&
     ++	git remote set-head fetch_upstream main &&
     ++	git -C fetch_upstream checkout -b fetch_unrelated &&
     ++	test_commit -C fetch_upstream u_unrelated_pre &&
     ++	git fetch fetch_upstream fetch_unrelated &&
     ++	unrelated_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_unrelated) &&
     ++	git -C fetch_upstream checkout main &&
     ++	test_commit -C fetch_upstream u_main_post &&
     ++	git -C fetch_upstream checkout fetch_unrelated &&
     ++	test_commit -C fetch_upstream u_unrelated_post &&
      +	git checkout --track=fetch -b local_from_remote fetch_upstream &&
     -+	git rev-parse --verify refs/remotes/fetch_upstream/fetch_new2
     ++	test_cmp_rev refs/remotes/fetch_upstream/main HEAD &&
     ++	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_unrelated)" = "$unrelated_before"
      +'
      +
     -+test_expect_success 'checkout --track=fetch aborts and does not create branch on fetch failure' '
     ++test_expect_success 'checkout --track=fetch aborts and does not create branch when no existing ref' '
      +	git checkout main &&
      +	test_might_fail git branch -D bogus &&
      +	test_must_fail git checkout --track=fetch -b bogus fetch_upstream/does_not_exist &&
      +	test_must_fail git rev-parse --verify refs/heads/bogus
      +'
      +
     ++test_expect_success 'checkout --track=fetch warns and proceeds when fetch fails but ref exists' '
     ++	git checkout main &&
     ++	git -C fetch_upstream checkout -b fetch_offline &&
     ++	test_commit -C fetch_upstream u_offline &&
     ++	git fetch fetch_upstream fetch_offline &&
     ++	saved_url=$(git config remote.fetch_upstream.url) &&
     ++	test_when_finished "git config remote.fetch_upstream.url \"$saved_url\"" &&
     ++	git config remote.fetch_upstream.url ./does-not-exist &&
     ++	git checkout --track=fetch -b local_offline fetch_upstream/fetch_offline 2>err &&
     ++	test_grep "failed to fetch" err &&
     ++	test_cmp_rev refs/remotes/fetch_upstream/fetch_offline HEAD
     ++'
     ++
     ++test_expect_success 'checkout --track=fetch resolves through configured fetch refspec' '
     ++	git checkout main &&
     ++	git -C fetch_upstream checkout -b fetch_refspec &&
     ++	test_commit -C fetch_upstream u_refspec &&
     ++	git fetch fetch_upstream fetch_refspec &&
     ++	git remote add fetch_custom ./fetch_upstream &&
     ++	test_when_finished "git remote remove fetch_custom" &&
     ++	git config --replace-all remote.fetch_custom.fetch \
     ++		"+refs/heads/*:refs/remotes/custom-ns/*" &&
     ++	git fetch fetch_custom &&
     ++	test_commit -C fetch_upstream u_refspec_post &&
     ++	git checkout --track=fetch -b local_refspec custom-ns/fetch_refspec &&
     ++	test_cmp_rev refs/remotes/custom-ns/fetch_refspec HEAD
     ++'
     ++
     ++test_expect_success 'checkout --track=inherit,direct is rejected' '
     ++	test_must_fail git checkout --track=inherit,direct -b bad fetch_upstream/fetch_new 2>err &&
     ++	test_grep "cannot combine" err
     ++'
     ++
     ++test_expect_success 'checkout --track=fetch then --track=direct drops fetch (last-one-wins)' '
     ++	git checkout main &&
     ++	git -C fetch_upstream checkout -b fetch_lastwin &&
     ++	test_commit -C fetch_upstream u_lastwin &&
     ++	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_lastwin &&
     ++	test_must_fail git checkout --track=fetch --track=direct \
     ++		-b local_lastwin fetch_upstream/fetch_lastwin &&
     ++	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_lastwin
     ++'
     ++
      +test_expect_success 'checkout --track=fetch,inherit fetches and inherits' '
      +	git checkout main &&
      +	git -C fetch_upstream checkout -b fetch_inherit &&


 Documentation/git-checkout.adoc |  13 ++-
 Documentation/git-switch.adoc   |  13 ++-
 builtin/checkout.c              | 168 +++++++++++++++++++++++++++++++-
 t/t7201-co.sh                   | 132 +++++++++++++++++++++++++
 4 files changed, 319 insertions(+), 7 deletions(-)

diff --git a/Documentation/git-checkout.adoc b/Documentation/git-checkout.adoc
index 43ccf47cf6..28f17f427e 100644
--- a/Documentation/git-checkout.adoc
+++ b/Documentation/git-checkout.adoc
@@ -158,11 +158,22 @@ of it").
 	resets _<branch>_ to the start point instead of failing.
 
 `-t`::
-`--track[=(direct|inherit)]`::
+`--track[=(direct|inherit|fetch)[,...]]`::
 	When creating a new branch, set up "upstream" configuration. See
 	`--track` in linkgit:git-branch[1] for details. As a convenience,
 	--track without -b implies branch creation.
 +
+The argument is a comma-separated list. `direct` (the default) and
+`inherit` select the tracking mode and are mutually exclusive. Adding
+`fetch` requests that the remote be fetched before _<start-point>_ is
+resolved, so the new branch starts from a fresh tip: when
+_<start-point>_ is in _<remote>/<branch>_ form, only that branch is
+updated; when _<start-point>_ is a bare remote name (e.g. `origin`),
+only the remote's default branch is updated. If the fetch fails and the
+corresponding remote-tracking ref already exists, a warning is printed
+and the checkout proceeds from the existing tip; otherwise the checkout
+is aborted.
++
 If no `-b` option is given, the name of the new branch will be
 derived from the remote-tracking branch, by looking at the local part of
 the refspec configured for the corresponding remote, and then stripping
diff --git a/Documentation/git-switch.adoc b/Documentation/git-switch.adoc
index 87707e9265..3f54cf39e9 100644
--- a/Documentation/git-switch.adoc
+++ b/Documentation/git-switch.adoc
@@ -154,11 +154,22 @@ should result in deletion of the path).
 	attached to a terminal, regardless of `--quiet`.
 
 `-t`::
-`--track[ (direct|inherit)]`::
+`--track[=(direct|inherit|fetch)[,...]]`::
 	When creating a new branch, set up "upstream" configuration.
 	`-c` is implied. See `--track` in linkgit:git-branch[1] for
 	details.
 +
+The argument is a comma-separated list. `direct` (the default) and
+`inherit` select the tracking mode and are mutually exclusive. Adding
+`fetch` requests that the remote be fetched before _<start-point>_ is
+resolved, so the new branch starts from a fresh tip: when
+_<start-point>_ is in _<remote>/<branch>_ form, only that branch is
+updated; when _<start-point>_ is a bare remote name (e.g. `origin`),
+only the remote's default branch is updated. If the fetch fails and the
+corresponding remote-tracking ref already exists, a warning is printed
+and the switch proceeds from the existing tip; otherwise the switch is
+aborted.
++
 If no `-c` option is given, the name of the new branch will be derived
 from the remote-tracking branch, by looking at the local part of the
 refspec configured for the corresponding remote, and then stripping
diff --git a/builtin/checkout.c b/builtin/checkout.c
index e031e61886..8f8d1ecffe 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -26,11 +26,14 @@
 #include "preload-index.h"
 #include "read-cache.h"
 #include "refs.h"
+#include "refspec.h"
 #include "remote.h"
 #include "repo-settings.h"
 #include "resolve-undo.h"
 #include "revision.h"
+#include "run-command.h"
 #include "setup.h"
+#include "strvec.h"
 #include "submodule.h"
 #include "symlinks.h"
 #include "trace2.h"
@@ -61,6 +64,7 @@ struct checkout_opts {
 	int count_checkout_paths;
 	int overlay_mode;
 	int dwim_new_local_branch;
+	int fetch;
 	int discard_changes;
 	int accept_ref;
 	int accept_pathspec;
@@ -112,6 +116,156 @@ struct branch_info {
 	char *checkout;
 };
 
+static int resolve_fetch_target(const char *arg, char **remote_out,
+				char **src_ref_out)
+{
+	const char *slash;
+	char *remote_name;
+	struct remote *remote;
+	struct refspec_item query = { 0 };
+	struct strbuf dst = STRBUF_INIT;
+	const char *rest;
+
+	*remote_out = NULL;
+	*src_ref_out = NULL;
+
+	if (!arg || !*arg)
+		return -1;
+
+	slash = strchr(arg, '/');
+	if (slash == arg)
+		return -1;
+	remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
+
+	remote = remote_get(remote_name);
+	if (!remote || !remote_is_configured(remote, 1)) {
+		free(remote_name);
+		return -1;
+	}
+
+	rest = (slash && slash[1]) ? slash + 1 : NULL;
+	if (!rest) {
+		struct object_id oid;
+		const char *head_target;
+		const char *short_target;
+
+		strbuf_addf(&dst, "refs/remotes/%s/HEAD", remote_name);
+		head_target = refs_resolve_ref_unsafe(get_main_ref_store(the_repository),
+						      dst.buf,
+						      RESOLVE_REF_READING |
+						      RESOLVE_REF_NO_RECURSE,
+						      &oid, NULL);
+		strbuf_reset(&dst);
+		if (head_target &&
+		    skip_prefix(head_target, "refs/remotes/", &short_target) &&
+		    skip_prefix(short_target, remote_name, &short_target) &&
+		    *short_target == '/')
+			rest = short_target + 1;
+	}
+
+	if (rest) {
+		strbuf_addf(&dst, "refs/remotes/%s/%s", remote_name, rest);
+		query.dst = dst.buf;
+		if (!remote_find_tracking(remote, &query) && query.src) {
+			*src_ref_out = xstrdup(query.src);
+			free(query.src);
+		} else {
+			*src_ref_out = xstrdup(rest);
+		}
+	}
+
+	strbuf_release(&dst);
+	*remote_out = remote_name;
+	return 0;
+}
+
+static void fetch_remote_for_start_point(const char *arg)
+{
+	char *remote_name = NULL;
+	char *src_ref = NULL;
+	struct child_process cmd = CHILD_PROCESS_INIT;
+	struct strbuf dst_ref = STRBUF_INIT;
+	int have_existing_ref = 0;
+
+	if (resolve_fetch_target(arg, &remote_name, &src_ref))
+		return;
+
+	if (src_ref) {
+		const char *short_src = src_ref;
+		struct object_id oid;
+
+		skip_prefix(short_src, "refs/heads/", &short_src);
+		strbuf_addf(&dst_ref, "refs/remotes/%s/%s", remote_name, short_src);
+		if (!refs_read_ref(get_main_ref_store(the_repository),
+				   dst_ref.buf, &oid))
+			have_existing_ref = 1;
+	}
+
+	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
+	if (src_ref)
+		strvec_push(&cmd.args, src_ref);
+	cmd.git_cmd = 1;
+	if (run_command(&cmd)) {
+		if (have_existing_ref)
+			warning(_("failed to fetch start-point '%s'; "
+				  "using existing '%s'"),
+				arg, dst_ref.buf);
+		else
+			die(_("failed to fetch start-point '%s'"), arg);
+	}
+
+	free(remote_name);
+	free(src_ref);
+	strbuf_release(&dst_ref);
+}
+
+static int parse_opt_checkout_track(const struct option *opt,
+				    const char *arg, int unset)
+{
+	struct checkout_opts *opts = opt->value;
+	struct string_list tokens = STRING_LIST_INIT_DUP;
+	struct string_list_item *item;
+	int saw_direct = 0, saw_inherit = 0;
+	int ret = 0;
+
+	opts->fetch = 0;
+
+	if (unset) {
+		opts->track = BRANCH_TRACK_NEVER;
+		return 0;
+	}
+
+	opts->track = BRANCH_TRACK_EXPLICIT;
+	if (!arg)
+		return 0;
+
+	string_list_split(&tokens, arg, ",", -1);
+	for_each_string_list_item(item, &tokens) {
+		if (!strcmp(item->string, "fetch")) {
+			opts->fetch = 1;
+		} else if (!strcmp(item->string, "direct")) {
+			saw_direct = 1;
+			opts->track = BRANCH_TRACK_EXPLICIT;
+		} else if (!strcmp(item->string, "inherit")) {
+			saw_inherit = 1;
+			opts->track = BRANCH_TRACK_INHERIT;
+		} else {
+			ret = error(_("option `%s' expects \"%s\", \"%s\", "
+				      "or \"%s\""),
+				    "--track", "direct", "inherit", "fetch");
+			goto out;
+		}
+	}
+
+	if (saw_direct && saw_inherit)
+		ret = error(_("option `%s' cannot combine \"%s\" and \"%s\""),
+			    "--track", "direct", "inherit");
+
+out:
+	string_list_clear(&tokens, 0);
+	return ret;
+}
+
 static void branch_info_release(struct branch_info *info)
 {
 	free(info->name);
@@ -1237,7 +1391,6 @@ static int git_checkout_config(const char *var, const char *value,
 		opts->dwim_new_local_branch = git_config_bool(var, value);
 		return 0;
 	}
-
 	if (starts_with(var, "submodule."))
 		return git_default_submodule_config(var, value, NULL);
 
@@ -1734,10 +1887,10 @@ static struct option *add_common_switch_branch_options(
 {
 	struct option options[] = {
 		OPT_BOOL('d', "detach", &opts->force_detach, N_("detach HEAD at named commit")),
-		OPT_CALLBACK_F('t', "track",  &opts->track, "(direct|inherit)",
+		OPT_CALLBACK_F('t', "track",  opts, "(direct|inherit|fetch)[,...]",
 			N_("set branch tracking configuration"),
 			PARSE_OPT_OPTARG,
-			parse_opt_tracking_mode),
+			parse_opt_checkout_track),
 		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
 			   PARSE_OPT_NOCOMPLETE),
 		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unborn branch")),
@@ -1942,8 +2095,13 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 			opts->dwim_new_local_branch &&
 			opts->track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts->new_branch;
-		int n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
-					     &new_branch_info, opts, &rev);
+		int n;
+
+		if (opts->fetch)
+			fetch_remote_for_start_point(argv[0]);
+
+		n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
+					 &new_branch_info, opts, &rev);
 		argv += n;
 		argc -= n;
 	} else if (!opts->accept_ref && opts->from_treeish) {
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 9bcf7c0b40..19ac6a1a2e 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -801,4 +801,136 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
 	test_cmp_config "" --default "" branch.main2.merge
 '
 
+test_expect_success 'setup upstream for --track=fetch tests' '
+	git checkout main &&
+	git init fetch_upstream &&
+	test_commit -C fetch_upstream u_main &&
+	git remote add fetch_upstream fetch_upstream &&
+	git fetch fetch_upstream &&
+	git -C fetch_upstream checkout -b fetch_new &&
+	test_commit -C fetch_upstream u_new
+'
+
+test_expect_success 'checkout --track=fetch -b picks up branch created upstream after clone' '
+	git checkout main &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
+	git checkout --track=fetch -b local_new fetch_upstream/fetch_new &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD &&
+	test_cmp_config fetch_upstream branch.local_new.remote &&
+	test_cmp_config refs/heads/fetch_new branch.local_new.merge
+'
+
+test_expect_success 'checkout --track=fetch <remote>/<branch> leaves other tracking branches untouched' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_target &&
+	test_commit -C fetch_upstream u_target_pre &&
+	git -C fetch_upstream checkout -b fetch_other &&
+	test_commit -C fetch_upstream u_other_pre &&
+	git fetch fetch_upstream &&
+	other_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_other) &&
+	git -C fetch_upstream checkout fetch_target &&
+	test_commit -C fetch_upstream u_target_post &&
+	git -C fetch_upstream checkout fetch_other &&
+	test_commit -C fetch_upstream u_other_post &&
+	git checkout --track=fetch -b local_target fetch_upstream/fetch_target &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_target HEAD &&
+	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before"
+'
+
+test_expect_success 'checkout --track=fetch with bare remote name fetches only <remote>/HEAD target' '
+	git checkout main &&
+	git -C fetch_upstream checkout main &&
+	git remote set-head fetch_upstream main &&
+	git -C fetch_upstream checkout -b fetch_unrelated &&
+	test_commit -C fetch_upstream u_unrelated_pre &&
+	git fetch fetch_upstream fetch_unrelated &&
+	unrelated_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_unrelated) &&
+	git -C fetch_upstream checkout main &&
+	test_commit -C fetch_upstream u_main_post &&
+	git -C fetch_upstream checkout fetch_unrelated &&
+	test_commit -C fetch_upstream u_unrelated_post &&
+	git checkout --track=fetch -b local_from_remote fetch_upstream &&
+	test_cmp_rev refs/remotes/fetch_upstream/main HEAD &&
+	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_unrelated)" = "$unrelated_before"
+'
+
+test_expect_success 'checkout --track=fetch aborts and does not create branch when no existing ref' '
+	git checkout main &&
+	test_might_fail git branch -D bogus &&
+	test_must_fail git checkout --track=fetch -b bogus fetch_upstream/does_not_exist &&
+	test_must_fail git rev-parse --verify refs/heads/bogus
+'
+
+test_expect_success 'checkout --track=fetch warns and proceeds when fetch fails but ref exists' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_offline &&
+	test_commit -C fetch_upstream u_offline &&
+	git fetch fetch_upstream fetch_offline &&
+	saved_url=$(git config remote.fetch_upstream.url) &&
+	test_when_finished "git config remote.fetch_upstream.url \"$saved_url\"" &&
+	git config remote.fetch_upstream.url ./does-not-exist &&
+	git checkout --track=fetch -b local_offline fetch_upstream/fetch_offline 2>err &&
+	test_grep "failed to fetch" err &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_offline HEAD
+'
+
+test_expect_success 'checkout --track=fetch resolves through configured fetch refspec' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_refspec &&
+	test_commit -C fetch_upstream u_refspec &&
+	git fetch fetch_upstream fetch_refspec &&
+	git remote add fetch_custom ./fetch_upstream &&
+	test_when_finished "git remote remove fetch_custom" &&
+	git config --replace-all remote.fetch_custom.fetch \
+		"+refs/heads/*:refs/remotes/custom-ns/*" &&
+	git fetch fetch_custom &&
+	test_commit -C fetch_upstream u_refspec_post &&
+	git checkout --track=fetch -b local_refspec custom-ns/fetch_refspec &&
+	test_cmp_rev refs/remotes/custom-ns/fetch_refspec HEAD
+'
+
+test_expect_success 'checkout --track=inherit,direct is rejected' '
+	test_must_fail git checkout --track=inherit,direct -b bad fetch_upstream/fetch_new 2>err &&
+	test_grep "cannot combine" err
+'
+
+test_expect_success 'checkout --track=fetch then --track=direct drops fetch (last-one-wins)' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_lastwin &&
+	test_commit -C fetch_upstream u_lastwin &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_lastwin &&
+	test_must_fail git checkout --track=fetch --track=direct \
+		-b local_lastwin fetch_upstream/fetch_lastwin &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_lastwin
+'
+
+test_expect_success 'checkout --track=fetch,inherit fetches and inherits' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_inherit &&
+	test_commit -C fetch_upstream u_inherit &&
+	git fetch fetch_upstream fetch_inherit &&
+	git checkout -b base_inherit fetch_upstream/fetch_inherit &&
+	test_commit -C fetch_upstream u_inherit2 &&
+	git checkout main &&
+	git checkout --track=fetch,inherit -b local_inherit base_inherit &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_inherit HEAD &&
+	test_cmp_config fetch_upstream branch.local_inherit.remote &&
+	test_cmp_config refs/heads/fetch_inherit branch.local_inherit.merge
+'
+
+test_expect_success 'checkout --track=bogus reports an error' '
+	git checkout main &&
+	test_must_fail git checkout --track=bogus -b bogus_branch fetch_upstream/fetch_new 2>err &&
+	test_grep "expects" err
+'
+
+test_expect_success 'switch --track=fetch -c picks up branch created upstream after clone' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_switch &&
+	test_commit -C fetch_upstream u_switch &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
+	git switch --track=fetch -c local_switch fetch_upstream/fetch_switch &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
+'
+
 test_done

base-commit: 94f057755b7941b321fd11fec1b2e3ca5313a4e0
-- 
gitgitgadget

Re: [PATCH v7] checkout: extend --track with a "fetch" mode to refresh start-point

[Phillip Wood]

Hi Harald

On 08/05/2026 23:52, Harald Nordgren via GitGitGadget wrote:
> From: Harald Nordgren <haraldnordgren@gmail.com>
> 
> +static void fetch_remote_for_start_point(const char *arg)
> +{
> +	char *remote_name = NULL;
> +	char *src_ref = NULL;
> +	struct child_process cmd = CHILD_PROCESS_INIT;
> +	struct strbuf dst_ref = STRBUF_INIT;
> +	int have_existing_ref = 0;
> +
> +	if (resolve_fetch_target(arg, &remote_name, &src_ref))
> +		return;
> +
> +	if (src_ref) {
> +		const char *short_src = src_ref;
> +		struct object_id oid;
> +
> +		skip_prefix(short_src, "refs/heads/", &short_src);
> +		strbuf_addf(&dst_ref, "refs/remotes/%s/%s", remote_name, short_src);
> +		if (!refs_read_ref(get_main_ref_store(the_repository),
> +				   dst_ref.buf, &oid))
> +			have_existing_ref = 1;

src_ref is the name of the branch on the remote server, not the name of 
the remote tracking ref which is given by arg. If arg is a remote name 
then we need to resolve refs/remotes/$arg/HEAD to find the branch to 
check, otherwise we should be checking refs/remotes/$arg

I've only given this version a quick scan through, but I didn't notice 
any other issues.

Thanks

Phillip

> +	}
> +
> +	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
> +	if (src_ref)
> +		strvec_push(&cmd.args, src_ref);
> +	cmd.git_cmd = 1;
> +	if (run_command(&cmd)) {
> +		if (have_existing_ref)
> +			warning(_("failed to fetch start-point '%s'; "
> +				  "using existing '%s'"),
> +				arg, dst_ref.buf);
> +		else
> +			die(_("failed to fetch start-point '%s'"), arg);
> +	}
> +
> +	free(remote_name);
> +	free(src_ref);
> +	strbuf_release(&dst_ref);
> +}
> +
> +static int parse_opt_checkout_track(const struct option *opt,
> +				    const char *arg, int unset)
> +{
> +	struct checkout_opts *opts = opt->value;
> +	struct string_list tokens = STRING_LIST_INIT_DUP;
> +	struct string_list_item *item;
> +	int saw_direct = 0, saw_inherit = 0;
> +	int ret = 0;
> +
> +	opts->fetch = 0;
> +
> +	if (unset) {
> +		opts->track = BRANCH_TRACK_NEVER;
> +		return 0;
> +	}
> +
> +	opts->track = BRANCH_TRACK_EXPLICIT;
> +	if (!arg)
> +		return 0;
> +
> +	string_list_split(&tokens, arg, ",", -1);
> +	for_each_string_list_item(item, &tokens) {
> +		if (!strcmp(item->string, "fetch")) {
> +			opts->fetch = 1;
> +		} else if (!strcmp(item->string, "direct")) {
> +			saw_direct = 1;
> +			opts->track = BRANCH_TRACK_EXPLICIT;
> +		} else if (!strcmp(item->string, "inherit")) {
> +			saw_inherit = 1;
> +			opts->track = BRANCH_TRACK_INHERIT;
> +		} else {
> +			ret = error(_("option `%s' expects \"%s\", \"%s\", "
> +				      "or \"%s\""),
> +				    "--track", "direct", "inherit", "fetch");
> +			goto out;
> +		}
> +	}
> +
> +	if (saw_direct && saw_inherit)
> +		ret = error(_("option `%s' cannot combine \"%s\" and \"%s\""),
> +			    "--track", "direct", "inherit");
> +
> +out:
> +	string_list_clear(&tokens, 0);
> +	return ret;
> +}
> +
>   static void branch_info_release(struct branch_info *info)
>   {
>   	free(info->name);
> @@ -1237,7 +1391,6 @@ static int git_checkout_config(const char *var, const char *value,
>   		opts->dwim_new_local_branch = git_config_bool(var, value);
>   		return 0;
>   	}
> -
>   	if (starts_with(var, "submodule."))
>   		return git_default_submodule_config(var, value, NULL);
>   
> @@ -1734,10 +1887,10 @@ static struct option *add_common_switch_branch_options(
>   {
>   	struct option options[] = {
>   		OPT_BOOL('d', "detach", &opts->force_detach, N_("detach HEAD at named commit")),
> -		OPT_CALLBACK_F('t', "track",  &opts->track, "(direct|inherit)",
> +		OPT_CALLBACK_F('t', "track",  opts, "(direct|inherit|fetch)[,...]",
>   			N_("set branch tracking configuration"),
>   			PARSE_OPT_OPTARG,
> -			parse_opt_tracking_mode),
> +			parse_opt_checkout_track),
>   		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
>   			   PARSE_OPT_NOCOMPLETE),
>   		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unborn branch")),
> @@ -1942,8 +2095,13 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
>   			opts->dwim_new_local_branch &&
>   			opts->track == BRANCH_TRACK_UNSPECIFIED &&
>   			!opts->new_branch;
> -		int n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
> -					     &new_branch_info, opts, &rev);
> +		int n;
> +
> +		if (opts->fetch)
> +			fetch_remote_for_start_point(argv[0]);
> +
> +		n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
> +					 &new_branch_info, opts, &rev);
>   		argv += n;
>   		argc -= n;
>   	} else if (!opts->accept_ref && opts->from_treeish) {
> diff --git a/t/t7201-co.sh b/t/t7201-co.sh
> index 9bcf7c0b40..19ac6a1a2e 100755
> --- a/t/t7201-co.sh
> +++ b/t/t7201-co.sh
> @@ -801,4 +801,136 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
>   	test_cmp_config "" --default "" branch.main2.merge
>   '
>   
> +test_expect_success 'setup upstream for --track=fetch tests' '
> +	git checkout main &&
> +	git init fetch_upstream &&
> +	test_commit -C fetch_upstream u_main &&
> +	git remote add fetch_upstream fetch_upstream &&
> +	git fetch fetch_upstream &&
> +	git -C fetch_upstream checkout -b fetch_new &&
> +	test_commit -C fetch_upstream u_new
> +'
> +
> +test_expect_success 'checkout --track=fetch -b picks up branch created upstream after clone' '
> +	git checkout main &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
> +	git checkout --track=fetch -b local_new fetch_upstream/fetch_new &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD &&
> +	test_cmp_config fetch_upstream branch.local_new.remote &&
> +	test_cmp_config refs/heads/fetch_new branch.local_new.merge
> +'
> +
> +test_expect_success 'checkout --track=fetch <remote>/<branch> leaves other tracking branches untouched' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_target &&
> +	test_commit -C fetch_upstream u_target_pre &&
> +	git -C fetch_upstream checkout -b fetch_other &&
> +	test_commit -C fetch_upstream u_other_pre &&
> +	git fetch fetch_upstream &&
> +	other_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_other) &&
> +	git -C fetch_upstream checkout fetch_target &&
> +	test_commit -C fetch_upstream u_target_post &&
> +	git -C fetch_upstream checkout fetch_other &&
> +	test_commit -C fetch_upstream u_other_post &&
> +	git checkout --track=fetch -b local_target fetch_upstream/fetch_target &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_target HEAD &&
> +	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before"
> +'
> +
> +test_expect_success 'checkout --track=fetch with bare remote name fetches only <remote>/HEAD target' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout main &&
> +	git remote set-head fetch_upstream main &&
> +	git -C fetch_upstream checkout -b fetch_unrelated &&
> +	test_commit -C fetch_upstream u_unrelated_pre &&
> +	git fetch fetch_upstream fetch_unrelated &&
> +	unrelated_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_unrelated) &&
> +	git -C fetch_upstream checkout main &&
> +	test_commit -C fetch_upstream u_main_post &&
> +	git -C fetch_upstream checkout fetch_unrelated &&
> +	test_commit -C fetch_upstream u_unrelated_post &&
> +	git checkout --track=fetch -b local_from_remote fetch_upstream &&
> +	test_cmp_rev refs/remotes/fetch_upstream/main HEAD &&
> +	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_unrelated)" = "$unrelated_before"
> +'
> +
> +test_expect_success 'checkout --track=fetch aborts and does not create branch when no existing ref' '
> +	git checkout main &&
> +	test_might_fail git branch -D bogus &&
> +	test_must_fail git checkout --track=fetch -b bogus fetch_upstream/does_not_exist &&
> +	test_must_fail git rev-parse --verify refs/heads/bogus
> +'
> +
> +test_expect_success 'checkout --track=fetch warns and proceeds when fetch fails but ref exists' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_offline &&
> +	test_commit -C fetch_upstream u_offline &&
> +	git fetch fetch_upstream fetch_offline &&
> +	saved_url=$(git config remote.fetch_upstream.url) &&
> +	test_when_finished "git config remote.fetch_upstream.url \"$saved_url\"" &&
> +	git config remote.fetch_upstream.url ./does-not-exist &&
> +	git checkout --track=fetch -b local_offline fetch_upstream/fetch_offline 2>err &&
> +	test_grep "failed to fetch" err &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_offline HEAD
> +'
> +
> +test_expect_success 'checkout --track=fetch resolves through configured fetch refspec' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_refspec &&
> +	test_commit -C fetch_upstream u_refspec &&
> +	git fetch fetch_upstream fetch_refspec &&
> +	git remote add fetch_custom ./fetch_upstream &&
> +	test_when_finished "git remote remove fetch_custom" &&
> +	git config --replace-all remote.fetch_custom.fetch \
> +		"+refs/heads/*:refs/remotes/custom-ns/*" &&
> +	git fetch fetch_custom &&
> +	test_commit -C fetch_upstream u_refspec_post &&
> +	git checkout --track=fetch -b local_refspec custom-ns/fetch_refspec &&
> +	test_cmp_rev refs/remotes/custom-ns/fetch_refspec HEAD
> +'
> +
> +test_expect_success 'checkout --track=inherit,direct is rejected' '
> +	test_must_fail git checkout --track=inherit,direct -b bad fetch_upstream/fetch_new 2>err &&
> +	test_grep "cannot combine" err
> +'
> +
> +test_expect_success 'checkout --track=fetch then --track=direct drops fetch (last-one-wins)' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_lastwin &&
> +	test_commit -C fetch_upstream u_lastwin &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_lastwin &&
> +	test_must_fail git checkout --track=fetch --track=direct \
> +		-b local_lastwin fetch_upstream/fetch_lastwin &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_lastwin
> +'
> +
> +test_expect_success 'checkout --track=fetch,inherit fetches and inherits' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_inherit &&
> +	test_commit -C fetch_upstream u_inherit &&
> +	git fetch fetch_upstream fetch_inherit &&
> +	git checkout -b base_inherit fetch_upstream/fetch_inherit &&
> +	test_commit -C fetch_upstream u_inherit2 &&
> +	git checkout main &&
> +	git checkout --track=fetch,inherit -b local_inherit base_inherit &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_inherit HEAD &&
> +	test_cmp_config fetch_upstream branch.local_inherit.remote &&
> +	test_cmp_config refs/heads/fetch_inherit branch.local_inherit.merge
> +'
> +
> +test_expect_success 'checkout --track=bogus reports an error' '
> +	git checkout main &&
> +	test_must_fail git checkout --track=bogus -b bogus_branch fetch_upstream/fetch_new 2>err &&
> +	test_grep "expects" err
> +'
> +
> +test_expect_success 'switch --track=fetch -c picks up branch created upstream after clone' '
> +	git checkout main &&
> +	git -C fetch_upstream checkout -b fetch_switch &&
> +	test_commit -C fetch_upstream u_switch &&
> +	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
> +	git switch --track=fetch -c local_switch fetch_upstream/fetch_switch &&
> +	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
> +'
> +
>   test_done
> 
> base-commit: 94f057755b7941b321fd11fec1b2e3ca5313a4e0

[PATCH v8] checkout: extend --track with a "fetch" mode to refresh start-point

[Harald Nordgren via GitGitGadget]

From: Harald Nordgren <haraldnordgren@gmail.com>

If you want to fork your topic branch from the very latest of the
tip of a branch your remote has, you would do:

    git fetch origin some-branch
    git checkout -b new_branch --track origin/some-branch

Extend the "--track" option of "git checkout" and allow users to
write

    git checkout -b new_branch --track=fetch origin/some-branch

to (1) fetch 'some-branch' from the remote 'origin', updating the
remote-tracking branch 'origin/some-branch', (2) arrange subsequent
'git pull' on 'new_branch' to interact with 'origin/some-branch' and
(3) fork 'new_branch' from it.

In the value of the '--track' option, 'fetch' can be combined with
the existing 'direct' (default) and 'inherit' modes via a
comma-separated list. Examples:

    git checkout -b new_branch --track=fetch,inherit some_local_branch
    git switch -c new_branch --track=fetch origin/some-branch

When "fetch" is requested and <start-point> is in <remote>/<branch>
form, run "git fetch <remote> <branch>" before resolving the ref, so
that other remote-tracking branches are left untouched. If
<start-point> is a bare remote name like "origin" (which resolves to
that remote's default branch), "git fetch <remote>" is run instead,
since the target branch is not known up front. Abort the checkout if
the fetch fails.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
    checkout: --track=fetch
    
    Check the fallback ref using arg directly instead of reconstructing it.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2281%2FHaraldNordgren%2Fcheckout-fetch-start-point-v8
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2281/HaraldNordgren/checkout-fetch-start-point-v8
Pull-Request: https://github.com/git/git/pull/2281

Range-diff vs v7:

 1:  de375d55f1 ! 1:  61c2199fd5 checkout: extend --track with a "fetch" mode to refresh start-point
     @@ builtin/checkout.c
       #include "revision.h"
      +#include "run-command.h"
       #include "setup.h"
     -+#include "strvec.h"
     + #include "strvec.h"
       #include "submodule.h"
     - #include "symlinks.h"
     - #include "trace2.h"
      @@ builtin/checkout.c: struct checkout_opts {
       	int count_checkout_paths;
       	int overlay_mode;
     @@ builtin/checkout.c: struct branch_info {
      +	if (resolve_fetch_target(arg, &remote_name, &src_ref))
      +		return;
      +
     -+	if (src_ref) {
     -+		const char *short_src = src_ref;
     ++	{
      +		struct object_id oid;
      +
     -+		skip_prefix(short_src, "refs/heads/", &short_src);
     -+		strbuf_addf(&dst_ref, "refs/remotes/%s/%s", remote_name, short_src);
     ++		if (strchr(arg, '/'))
     ++			strbuf_addf(&dst_ref, "refs/remotes/%s", arg);
     ++		else
     ++			strbuf_addf(&dst_ref, "refs/remotes/%s/HEAD", arg);
      +		if (!refs_read_ref(get_main_ref_store(the_repository),
      +				   dst_ref.buf, &oid))
      +			have_existing_ref = 1;


 Documentation/git-checkout.adoc |  13 ++-
 Documentation/git-switch.adoc   |  13 ++-
 builtin/checkout.c              | 168 +++++++++++++++++++++++++++++++-
 t/t7201-co.sh                   | 132 +++++++++++++++++++++++++
 4 files changed, 319 insertions(+), 7 deletions(-)

diff --git a/Documentation/git-checkout.adoc b/Documentation/git-checkout.adoc
index 43ccf47cf6..28f17f427e 100644
--- a/Documentation/git-checkout.adoc
+++ b/Documentation/git-checkout.adoc
@@ -158,11 +158,22 @@ of it").
 	resets _<branch>_ to the start point instead of failing.
 
 `-t`::
-`--track[=(direct|inherit)]`::
+`--track[=(direct|inherit|fetch)[,...]]`::
 	When creating a new branch, set up "upstream" configuration. See
 	`--track` in linkgit:git-branch[1] for details. As a convenience,
 	--track without -b implies branch creation.
 +
+The argument is a comma-separated list. `direct` (the default) and
+`inherit` select the tracking mode and are mutually exclusive. Adding
+`fetch` requests that the remote be fetched before _<start-point>_ is
+resolved, so the new branch starts from a fresh tip: when
+_<start-point>_ is in _<remote>/<branch>_ form, only that branch is
+updated; when _<start-point>_ is a bare remote name (e.g. `origin`),
+only the remote's default branch is updated. If the fetch fails and the
+corresponding remote-tracking ref already exists, a warning is printed
+and the checkout proceeds from the existing tip; otherwise the checkout
+is aborted.
++
 If no `-b` option is given, the name of the new branch will be
 derived from the remote-tracking branch, by looking at the local part of
 the refspec configured for the corresponding remote, and then stripping
diff --git a/Documentation/git-switch.adoc b/Documentation/git-switch.adoc
index 87707e9265..3f54cf39e9 100644
--- a/Documentation/git-switch.adoc
+++ b/Documentation/git-switch.adoc
@@ -154,11 +154,22 @@ should result in deletion of the path).
 	attached to a terminal, regardless of `--quiet`.
 
 `-t`::
-`--track[ (direct|inherit)]`::
+`--track[=(direct|inherit|fetch)[,...]]`::
 	When creating a new branch, set up "upstream" configuration.
 	`-c` is implied. See `--track` in linkgit:git-branch[1] for
 	details.
 +
+The argument is a comma-separated list. `direct` (the default) and
+`inherit` select the tracking mode and are mutually exclusive. Adding
+`fetch` requests that the remote be fetched before _<start-point>_ is
+resolved, so the new branch starts from a fresh tip: when
+_<start-point>_ is in _<remote>/<branch>_ form, only that branch is
+updated; when _<start-point>_ is a bare remote name (e.g. `origin`),
+only the remote's default branch is updated. If the fetch fails and the
+corresponding remote-tracking ref already exists, a warning is printed
+and the switch proceeds from the existing tip; otherwise the switch is
+aborted.
++
 If no `-c` option is given, the name of the new branch will be derived
 from the remote-tracking branch, by looking at the local part of the
 refspec configured for the corresponding remote, and then stripping
diff --git a/builtin/checkout.c b/builtin/checkout.c
index ac0186a33e..157242bc9f 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -26,10 +26,12 @@
 #include "preload-index.h"
 #include "read-cache.h"
 #include "refs.h"
+#include "refspec.h"
 #include "remote.h"
 #include "repo-settings.h"
 #include "resolve-undo.h"
 #include "revision.h"
+#include "run-command.h"
 #include "setup.h"
 #include "strvec.h"
 #include "submodule.h"
@@ -62,6 +64,7 @@ struct checkout_opts {
 	int count_checkout_paths;
 	int overlay_mode;
 	int dwim_new_local_branch;
+	int fetch;
 	int discard_changes;
 	int accept_ref;
 	int accept_pathspec;
@@ -113,6 +116,157 @@ struct branch_info {
 	char *checkout;
 };
 
+static int resolve_fetch_target(const char *arg, char **remote_out,
+				char **src_ref_out)
+{
+	const char *slash;
+	char *remote_name;
+	struct remote *remote;
+	struct refspec_item query = { 0 };
+	struct strbuf dst = STRBUF_INIT;
+	const char *rest;
+
+	*remote_out = NULL;
+	*src_ref_out = NULL;
+
+	if (!arg || !*arg)
+		return -1;
+
+	slash = strchr(arg, '/');
+	if (slash == arg)
+		return -1;
+	remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
+
+	remote = remote_get(remote_name);
+	if (!remote || !remote_is_configured(remote, 1)) {
+		free(remote_name);
+		return -1;
+	}
+
+	rest = (slash && slash[1]) ? slash + 1 : NULL;
+	if (!rest) {
+		struct object_id oid;
+		const char *head_target;
+		const char *short_target;
+
+		strbuf_addf(&dst, "refs/remotes/%s/HEAD", remote_name);
+		head_target = refs_resolve_ref_unsafe(get_main_ref_store(the_repository),
+						      dst.buf,
+						      RESOLVE_REF_READING |
+						      RESOLVE_REF_NO_RECURSE,
+						      &oid, NULL);
+		strbuf_reset(&dst);
+		if (head_target &&
+		    skip_prefix(head_target, "refs/remotes/", &short_target) &&
+		    skip_prefix(short_target, remote_name, &short_target) &&
+		    *short_target == '/')
+			rest = short_target + 1;
+	}
+
+	if (rest) {
+		strbuf_addf(&dst, "refs/remotes/%s/%s", remote_name, rest);
+		query.dst = dst.buf;
+		if (!remote_find_tracking(remote, &query) && query.src) {
+			*src_ref_out = xstrdup(query.src);
+			free(query.src);
+		} else {
+			*src_ref_out = xstrdup(rest);
+		}
+	}
+
+	strbuf_release(&dst);
+	*remote_out = remote_name;
+	return 0;
+}
+
+static void fetch_remote_for_start_point(const char *arg)
+{
+	char *remote_name = NULL;
+	char *src_ref = NULL;
+	struct child_process cmd = CHILD_PROCESS_INIT;
+	struct strbuf dst_ref = STRBUF_INIT;
+	int have_existing_ref = 0;
+
+	if (resolve_fetch_target(arg, &remote_name, &src_ref))
+		return;
+
+	{
+		struct object_id oid;
+
+		if (strchr(arg, '/'))
+			strbuf_addf(&dst_ref, "refs/remotes/%s", arg);
+		else
+			strbuf_addf(&dst_ref, "refs/remotes/%s/HEAD", arg);
+		if (!refs_read_ref(get_main_ref_store(the_repository),
+				   dst_ref.buf, &oid))
+			have_existing_ref = 1;
+	}
+
+	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
+	if (src_ref)
+		strvec_push(&cmd.args, src_ref);
+	cmd.git_cmd = 1;
+	if (run_command(&cmd)) {
+		if (have_existing_ref)
+			warning(_("failed to fetch start-point '%s'; "
+				  "using existing '%s'"),
+				arg, dst_ref.buf);
+		else
+			die(_("failed to fetch start-point '%s'"), arg);
+	}
+
+	free(remote_name);
+	free(src_ref);
+	strbuf_release(&dst_ref);
+}
+
+static int parse_opt_checkout_track(const struct option *opt,
+				    const char *arg, int unset)
+{
+	struct checkout_opts *opts = opt->value;
+	struct string_list tokens = STRING_LIST_INIT_DUP;
+	struct string_list_item *item;
+	int saw_direct = 0, saw_inherit = 0;
+	int ret = 0;
+
+	opts->fetch = 0;
+
+	if (unset) {
+		opts->track = BRANCH_TRACK_NEVER;
+		return 0;
+	}
+
+	opts->track = BRANCH_TRACK_EXPLICIT;
+	if (!arg)
+		return 0;
+
+	string_list_split(&tokens, arg, ",", -1);
+	for_each_string_list_item(item, &tokens) {
+		if (!strcmp(item->string, "fetch")) {
+			opts->fetch = 1;
+		} else if (!strcmp(item->string, "direct")) {
+			saw_direct = 1;
+			opts->track = BRANCH_TRACK_EXPLICIT;
+		} else if (!strcmp(item->string, "inherit")) {
+			saw_inherit = 1;
+			opts->track = BRANCH_TRACK_INHERIT;
+		} else {
+			ret = error(_("option `%s' expects \"%s\", \"%s\", "
+				      "or \"%s\""),
+				    "--track", "direct", "inherit", "fetch");
+			goto out;
+		}
+	}
+
+	if (saw_direct && saw_inherit)
+		ret = error(_("option `%s' cannot combine \"%s\" and \"%s\""),
+			    "--track", "direct", "inherit");
+
+out:
+	string_list_clear(&tokens, 0);
+	return ret;
+}
+
 static void branch_info_release(struct branch_info *info)
 {
 	free(info->name);
@@ -1244,7 +1398,6 @@ static int git_checkout_config(const char *var, const char *value,
 		opts->dwim_new_local_branch = git_config_bool(var, value);
 		return 0;
 	}
-
 	if (starts_with(var, "submodule."))
 		return git_default_submodule_config(var, value, NULL);
 
@@ -1741,10 +1894,10 @@ static struct option *add_common_switch_branch_options(
 {
 	struct option options[] = {
 		OPT_BOOL('d', "detach", &opts->force_detach, N_("detach HEAD at named commit")),
-		OPT_CALLBACK_F('t', "track",  &opts->track, "(direct|inherit)",
+		OPT_CALLBACK_F('t', "track",  opts, "(direct|inherit|fetch)[,...]",
 			N_("set branch tracking configuration"),
 			PARSE_OPT_OPTARG,
-			parse_opt_tracking_mode),
+			parse_opt_checkout_track),
 		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
 			   PARSE_OPT_NOCOMPLETE),
 		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unborn branch")),
@@ -1949,8 +2102,13 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 			opts->dwim_new_local_branch &&
 			opts->track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts->new_branch;
-		int n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
-					     &new_branch_info, opts, &rev);
+		int n;
+
+		if (opts->fetch)
+			fetch_remote_for_start_point(argv[0]);
+
+		n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
+					 &new_branch_info, opts, &rev);
 		argv += n;
 		argc -= n;
 	} else if (!opts->accept_ref && opts->from_treeish) {
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 9bcf7c0b40..19ac6a1a2e 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -801,4 +801,136 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
 	test_cmp_config "" --default "" branch.main2.merge
 '
 
+test_expect_success 'setup upstream for --track=fetch tests' '
+	git checkout main &&
+	git init fetch_upstream &&
+	test_commit -C fetch_upstream u_main &&
+	git remote add fetch_upstream fetch_upstream &&
+	git fetch fetch_upstream &&
+	git -C fetch_upstream checkout -b fetch_new &&
+	test_commit -C fetch_upstream u_new
+'
+
+test_expect_success 'checkout --track=fetch -b picks up branch created upstream after clone' '
+	git checkout main &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
+	git checkout --track=fetch -b local_new fetch_upstream/fetch_new &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD &&
+	test_cmp_config fetch_upstream branch.local_new.remote &&
+	test_cmp_config refs/heads/fetch_new branch.local_new.merge
+'
+
+test_expect_success 'checkout --track=fetch <remote>/<branch> leaves other tracking branches untouched' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_target &&
+	test_commit -C fetch_upstream u_target_pre &&
+	git -C fetch_upstream checkout -b fetch_other &&
+	test_commit -C fetch_upstream u_other_pre &&
+	git fetch fetch_upstream &&
+	other_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_other) &&
+	git -C fetch_upstream checkout fetch_target &&
+	test_commit -C fetch_upstream u_target_post &&
+	git -C fetch_upstream checkout fetch_other &&
+	test_commit -C fetch_upstream u_other_post &&
+	git checkout --track=fetch -b local_target fetch_upstream/fetch_target &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_target HEAD &&
+	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before"
+'
+
+test_expect_success 'checkout --track=fetch with bare remote name fetches only <remote>/HEAD target' '
+	git checkout main &&
+	git -C fetch_upstream checkout main &&
+	git remote set-head fetch_upstream main &&
+	git -C fetch_upstream checkout -b fetch_unrelated &&
+	test_commit -C fetch_upstream u_unrelated_pre &&
+	git fetch fetch_upstream fetch_unrelated &&
+	unrelated_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_unrelated) &&
+	git -C fetch_upstream checkout main &&
+	test_commit -C fetch_upstream u_main_post &&
+	git -C fetch_upstream checkout fetch_unrelated &&
+	test_commit -C fetch_upstream u_unrelated_post &&
+	git checkout --track=fetch -b local_from_remote fetch_upstream &&
+	test_cmp_rev refs/remotes/fetch_upstream/main HEAD &&
+	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_unrelated)" = "$unrelated_before"
+'
+
+test_expect_success 'checkout --track=fetch aborts and does not create branch when no existing ref' '
+	git checkout main &&
+	test_might_fail git branch -D bogus &&
+	test_must_fail git checkout --track=fetch -b bogus fetch_upstream/does_not_exist &&
+	test_must_fail git rev-parse --verify refs/heads/bogus
+'
+
+test_expect_success 'checkout --track=fetch warns and proceeds when fetch fails but ref exists' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_offline &&
+	test_commit -C fetch_upstream u_offline &&
+	git fetch fetch_upstream fetch_offline &&
+	saved_url=$(git config remote.fetch_upstream.url) &&
+	test_when_finished "git config remote.fetch_upstream.url \"$saved_url\"" &&
+	git config remote.fetch_upstream.url ./does-not-exist &&
+	git checkout --track=fetch -b local_offline fetch_upstream/fetch_offline 2>err &&
+	test_grep "failed to fetch" err &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_offline HEAD
+'
+
+test_expect_success 'checkout --track=fetch resolves through configured fetch refspec' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_refspec &&
+	test_commit -C fetch_upstream u_refspec &&
+	git fetch fetch_upstream fetch_refspec &&
+	git remote add fetch_custom ./fetch_upstream &&
+	test_when_finished "git remote remove fetch_custom" &&
+	git config --replace-all remote.fetch_custom.fetch \
+		"+refs/heads/*:refs/remotes/custom-ns/*" &&
+	git fetch fetch_custom &&
+	test_commit -C fetch_upstream u_refspec_post &&
+	git checkout --track=fetch -b local_refspec custom-ns/fetch_refspec &&
+	test_cmp_rev refs/remotes/custom-ns/fetch_refspec HEAD
+'
+
+test_expect_success 'checkout --track=inherit,direct is rejected' '
+	test_must_fail git checkout --track=inherit,direct -b bad fetch_upstream/fetch_new 2>err &&
+	test_grep "cannot combine" err
+'
+
+test_expect_success 'checkout --track=fetch then --track=direct drops fetch (last-one-wins)' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_lastwin &&
+	test_commit -C fetch_upstream u_lastwin &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_lastwin &&
+	test_must_fail git checkout --track=fetch --track=direct \
+		-b local_lastwin fetch_upstream/fetch_lastwin &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_lastwin
+'
+
+test_expect_success 'checkout --track=fetch,inherit fetches and inherits' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_inherit &&
+	test_commit -C fetch_upstream u_inherit &&
+	git fetch fetch_upstream fetch_inherit &&
+	git checkout -b base_inherit fetch_upstream/fetch_inherit &&
+	test_commit -C fetch_upstream u_inherit2 &&
+	git checkout main &&
+	git checkout --track=fetch,inherit -b local_inherit base_inherit &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_inherit HEAD &&
+	test_cmp_config fetch_upstream branch.local_inherit.remote &&
+	test_cmp_config refs/heads/fetch_inherit branch.local_inherit.merge
+'
+
+test_expect_success 'checkout --track=bogus reports an error' '
+	git checkout main &&
+	test_must_fail git checkout --track=bogus -b bogus_branch fetch_upstream/fetch_new 2>err &&
+	test_grep "expects" err
+'
+
+test_expect_success 'switch --track=fetch -c picks up branch created upstream after clone' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_switch &&
+	test_commit -C fetch_upstream u_switch &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
+	git switch --track=fetch -c local_switch fetch_upstream/fetch_switch &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
+'
+
 test_done

base-commit: 7760f83b59750c27df653c5c46d0f80e44cfe02c
-- 
gitgitgadget

Re: [PATCH v8] checkout: extend --track with a "fetch" mode to refresh start-point

[Junio C Hamano]

"Harald Nordgren via GitGitGadget" <gitgitgadget@gmail.com> writes:

> diff --git a/Documentation/git-checkout.adoc b/Documentation/git-checkout.adoc
> index 43ccf47cf6..28f17f427e 100644
> --- a/Documentation/git-checkout.adoc
> +++ b/Documentation/git-checkout.adoc
> @@ -158,11 +158,22 @@ of it").
>  	resets _<branch>_ to the start point instead of failing.
>  
>  `-t`::
> -`--track[=(direct|inherit)]`::
> +`--track[=(direct|inherit|fetch)[,...]]`::
>  	When creating a new branch, set up "upstream" configuration. See
>  	`--track` in linkgit:git-branch[1] for details. As a convenience,
>  	--track without -b implies branch creation.
>  +
> +The argument is a comma-separated list. `direct` (the default) and
> +`inherit` select the tracking mode and are mutually exclusive. Adding
> +`fetch` requests that the remote be fetched before _<start-point>_ is
> +resolved, so the new branch starts from a fresh tip: when
> +_<start-point>_ is in _<remote>/<branch>_ form, only that branch is
> +updated; when _<start-point>_ is a bare remote name (e.g. `origin`),
> +only the remote's default branch is updated.

The latter is because "checkout -t -b new remote/origin" makes "new"
track "remote/origin/HEAD", which makes sense.  And of course this
fetch can fail.

> +static int resolve_fetch_target(const char *arg, char **remote_out,
> +				char **src_ref_out)
> +{
> +	const char *slash;
> +	char *remote_name;
> +	struct remote *remote;
> +	struct refspec_item query = { 0 };
> +	struct strbuf dst = STRBUF_INIT;
> +	const char *rest;
> +
> +	*remote_out = NULL;
> +	*src_ref_out = NULL;
> +
> +	if (!arg || !*arg)
> +		return -1;
> +
> +	slash = strchr(arg, '/');
> +	if (slash == arg)
> +		return -1;
> +	remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
> +
> +	remote = remote_get(remote_name);
> +	if (!remote || !remote_is_configured(remote, 1)) {
> +		free(remote_name);
> +		return -1;
> +	}
> +
> +	rest = (slash && slash[1]) ? slash + 1 : NULL;

There is no slash when asking for "origin", and the control goes
into the "if (!rest)" block.

> +	if (!rest) {
> +		struct object_id oid;
> +		const char *head_target;
> +		const char *short_target;
> +
> +		strbuf_addf(&dst, "refs/remotes/%s/HEAD", remote_name);
> +		head_target = refs_resolve_ref_unsafe(get_main_ref_store(the_repository),
> +						      dst.buf,
> +						      RESOLVE_REF_READING |
> +						      RESOLVE_REF_NO_RECURSE,
> +						      &oid, NULL);
> +		strbuf_reset(&dst);
> +		if (head_target &&
> +		    skip_prefix(head_target, "refs/remotes/", &short_target) &&
> +		    skip_prefix(short_target, remote_name, &short_target) &&
> +		    *short_target == '/')
> +			rest = short_target + 1;
> +	}

If refs/remotes/origin/HEAD points at refs/remotes/origin/main, rest
gets "main".  Otherwise (i.e. unexpected contents in HEAD or lacking
HEAD), rest remains NULL.  And then we have the "if (rest)" block.

> +	if (rest) {
> +		strbuf_addf(&dst, "refs/remotes/%s/%s", remote_name, rest);
> +		query.dst = dst.buf;
> +		if (!remote_find_tracking(remote, &query) && query.src) {
> +			*src_ref_out = xstrdup(query.src);
> +			free(query.src);
> +		} else {
> +			*src_ref_out = xstrdup(rest);
> +		}
> +	}
> +
> +	strbuf_release(&dst);
> +	*remote_out = remote_name;
> +	return 0;
> +}

It is not a new problem but I do not remember how we explicitly
forbid "hierarchical" remote names.  refs/remotes/a/b/c might be
their branch "b/c" at remote we call "a", or branch "c" at remote
"a/b".  Unless we forbid slashes in remote names, the "there is no
slash so we got only the name of the remote to mean its HEAD" logic
would not work well, so we may want to double check.

> +static void fetch_remote_for_start_point(const char *arg)
> +{
> +	char *remote_name = NULL;
> +	char *src_ref = NULL;
> +	struct child_process cmd = CHILD_PROCESS_INIT;
> +	struct strbuf dst_ref = STRBUF_INIT;
> +	int have_existing_ref = 0;
> +
> +	if (resolve_fetch_target(arg, &remote_name, &src_ref))
> +		return;
> +
> +	{
> +		struct object_id oid;
> +
> +		if (strchr(arg, '/'))
> +			strbuf_addf(&dst_ref, "refs/remotes/%s", arg);
> +		else
> +			strbuf_addf(&dst_ref, "refs/remotes/%s/HEAD", arg);
> +		if (!refs_read_ref(get_main_ref_store(the_repository),
> +				   dst_ref.buf, &oid))
> +			have_existing_ref = 1;
> +	}

I do not quite see the point of this extra block.  Can we do without
it (and move the def of oid up near the beginning of the function,
of course)?

Even better, as resolve_fetch_target() already looks at "arg" and
poked at the remote-tracking ref hierarchy, wouldn't it make more
sense to make that helper function responsible for finding out if
there already is a usable, albeit potentially stale, ref?  


> +	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
> +	if (src_ref)
> +		strvec_push(&cmd.args, src_ref);
> +	cmd.git_cmd = 1;
> +	if (run_command(&cmd)) {
> +		if (have_existing_ref)
> +			warning(_("failed to fetch start-point '%s'; "
> +				  "using existing '%s'"),
> +				arg, dst_ref.buf);
> +		else
> +			die(_("failed to fetch start-point '%s'"), arg);
> +	}
> +
> +	free(remote_name);
> +	free(src_ref);
> +	strbuf_release(&dst_ref);
> +}

> @@ -1244,7 +1398,6 @@ static int git_checkout_config(const char *var, const char *value,
>  		opts->dwim_new_local_branch = git_config_bool(var, value);
>  		return 0;
>  	}
> -
>  	if (starts_with(var, "submodule."))
>  		return git_default_submodule_config(var, value, NULL);

Unrelated patch noise?

[PATCH v9] checkout: extend --track with a "fetch" mode to refresh start-point

[Harald Nordgren via GitGitGadget]

From: Harald Nordgren <haraldnordgren@gmail.com>

If you want to fork your topic branch from the very latest of the
tip of a branch your remote has, you would do:

    git fetch origin some-branch
    git checkout -b new_branch --track origin/some-branch

Extend the "--track" option of "git checkout" and allow users to
write

    git checkout -b new_branch --track=fetch origin/some-branch

to (1) fetch 'some-branch' from the remote 'origin', updating the
remote-tracking branch 'origin/some-branch', (2) arrange subsequent
'git pull' on 'new_branch' to interact with 'origin/some-branch' and
(3) fork 'new_branch' from it.

In the value of the '--track' option, 'fetch' can be combined with
the existing 'direct' (default) and 'inherit' modes via a
comma-separated list. Examples:

    git checkout -b new_branch --track=fetch,inherit some_local_branch
    git switch -c new_branch --track=fetch origin/some-branch

When "fetch" is requested and <start-point> is in <remote>/<branch>
form, run "git fetch <remote> <branch>" before resolving the ref, so
that other remote-tracking branches are left untouched. If
<start-point> is a bare remote name like "origin" (which resolves to
that remote's default branch), "git fetch <remote>" is run instead,
since the target branch is not known up front. Abort the checkout if
the fetch fails.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
    checkout: --track=fetch
    
     * Support hierarchical remote names (e.g. nested/remote) by trying the
       longest prefix first.
     * Fold the existing-ref lookup into resolve_fetch_target() so it
       returns the ref name directly.

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2281%2FHaraldNordgren%2Fcheckout-fetch-start-point-v9
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2281/HaraldNordgren/checkout-fetch-start-point-v9
Pull-Request: https://github.com/git/git/pull/2281

Range-diff vs v8:

 1:  61c2199fd5 ! 1:  021375e4cc checkout: extend --track with a "fetch" mode to refresh start-point
     @@ builtin/checkout.c: struct branch_info {
       };
       
      +static int resolve_fetch_target(const char *arg, char **remote_out,
     -+				char **src_ref_out)
     ++				char **src_ref_out, char **existing_ref_out)
      +{
      +	const char *slash;
     -+	char *remote_name;
     -+	struct remote *remote;
     ++	char *remote_name = NULL;
     ++	struct remote *remote = NULL;
      +	struct refspec_item query = { 0 };
      +	struct strbuf dst = STRBUF_INIT;
     -+	const char *rest;
     ++	struct object_id oid;
     ++	const char *rest = NULL;
     ++	const char *head_target = NULL;
     ++	const char *short_target;
      +
      +	*remote_out = NULL;
      +	*src_ref_out = NULL;
     ++	*existing_ref_out = NULL;
      +
     -+	if (!arg || !*arg)
     -+		return -1;
     -+
     -+	slash = strchr(arg, '/');
     -+	if (slash == arg)
     ++	if (!arg || !*arg || *arg == '/')
      +		return -1;
     -+	remote_name = slash ? xstrndup(arg, slash - arg) : xstrdup(arg);
      +
     -+	remote = remote_get(remote_name);
     -+	if (!remote || !remote_is_configured(remote, 1)) {
     ++	slash = arg + strlen(arg);
     ++	while (1) {
      +		free(remote_name);
     -+		return -1;
     ++		remote_name = xstrndup(arg, slash - arg);
     ++		remote = remote_get(remote_name);
     ++		if (remote && remote_is_configured(remote, 1))
     ++			break;
     ++		while (slash > arg && *--slash != '/')
     ++			;
     ++		if (slash == arg) {
     ++			free(remote_name);
     ++			return -1;
     ++		}
      +	}
      +
     -+	rest = (slash && slash[1]) ? slash + 1 : NULL;
     ++	if (*slash == '/' && slash[1])
     ++		rest = slash + 1;
      +	if (!rest) {
     -+		struct object_id oid;
     -+		const char *head_target;
     -+		const char *short_target;
     -+
      +		strbuf_addf(&dst, "refs/remotes/%s/HEAD", remote_name);
      +		head_target = refs_resolve_ref_unsafe(get_main_ref_store(the_repository),
      +						      dst.buf,
      +						      RESOLVE_REF_READING |
      +						      RESOLVE_REF_NO_RECURSE,
      +						      &oid, NULL);
     ++		if (head_target) {
     ++			*existing_ref_out = xstrdup(dst.buf);
     ++			if (skip_prefix(head_target, "refs/remotes/", &short_target) &&
     ++			    skip_prefix(short_target, remote_name, &short_target) &&
     ++			    *short_target == '/')
     ++				rest = short_target + 1;
     ++		}
      +		strbuf_reset(&dst);
     -+		if (head_target &&
     -+		    skip_prefix(head_target, "refs/remotes/", &short_target) &&
     -+		    skip_prefix(short_target, remote_name, &short_target) &&
     -+		    *short_target == '/')
     -+			rest = short_target + 1;
      +	}
      +
      +	if (rest) {
     @@ builtin/checkout.c: struct branch_info {
      +		} else {
      +			*src_ref_out = xstrdup(rest);
      +		}
     ++		if (!*existing_ref_out) {
     ++			strbuf_reset(&dst);
     ++			strbuf_addf(&dst, "refs/remotes/%s", arg);
     ++			if (!refs_read_ref(get_main_ref_store(the_repository),
     ++					   dst.buf, &oid))
     ++				*existing_ref_out = xstrdup(dst.buf);
     ++		}
      +	}
      +
      +	strbuf_release(&dst);
     @@ builtin/checkout.c: struct branch_info {
      +{
      +	char *remote_name = NULL;
      +	char *src_ref = NULL;
     ++	char *existing_ref = NULL;
      +	struct child_process cmd = CHILD_PROCESS_INIT;
     -+	struct strbuf dst_ref = STRBUF_INIT;
     -+	int have_existing_ref = 0;
      +
     -+	if (resolve_fetch_target(arg, &remote_name, &src_ref))
     ++	if (resolve_fetch_target(arg, &remote_name, &src_ref, &existing_ref))
      +		return;
      +
     -+	{
     -+		struct object_id oid;
     -+
     -+		if (strchr(arg, '/'))
     -+			strbuf_addf(&dst_ref, "refs/remotes/%s", arg);
     -+		else
     -+			strbuf_addf(&dst_ref, "refs/remotes/%s/HEAD", arg);
     -+		if (!refs_read_ref(get_main_ref_store(the_repository),
     -+				   dst_ref.buf, &oid))
     -+			have_existing_ref = 1;
     -+	}
     -+
      +	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
      +	if (src_ref)
      +		strvec_push(&cmd.args, src_ref);
      +	cmd.git_cmd = 1;
      +	if (run_command(&cmd)) {
     -+		if (have_existing_ref)
     ++		if (existing_ref)
      +			warning(_("failed to fetch start-point '%s'; "
      +				  "using existing '%s'"),
     -+				arg, dst_ref.buf);
     ++				arg, existing_ref);
      +		else
      +			die(_("failed to fetch start-point '%s'"), arg);
      +	}
      +
      +	free(remote_name);
      +	free(src_ref);
     -+	strbuf_release(&dst_ref);
     ++	free(existing_ref);
      +}
      +
      +static int parse_opt_checkout_track(const struct option *opt,
     @@ builtin/checkout.c: struct branch_info {
       static void branch_info_release(struct branch_info *info)
       {
       	free(info->name);
     -@@ builtin/checkout.c: static int git_checkout_config(const char *var, const char *value,
     - 		opts->dwim_new_local_branch = git_config_bool(var, value);
     - 		return 0;
     - 	}
     --
     - 	if (starts_with(var, "submodule."))
     - 		return git_default_submodule_config(var, value, NULL);
     - 
      @@ builtin/checkout.c: static struct option *add_common_switch_branch_options(
       {
       	struct option options[] = {
     @@ t/t7201-co.sh: test_expect_success 'tracking info copied with autoSetupMerge=inh
      +	test_cmp_rev refs/remotes/custom-ns/fetch_refspec HEAD
      +'
      +
     ++test_expect_success 'checkout --track=fetch handles hierarchical remote name' '
     ++	git checkout main &&
     ++	git -C fetch_upstream checkout -b fetch_hier &&
     ++	test_commit -C fetch_upstream u_hier &&
     ++	git remote add nested/remote ./fetch_upstream &&
     ++	test_when_finished "git remote remove nested/remote" &&
     ++	git fetch nested/remote fetch_hier &&
     ++	test_commit -C fetch_upstream u_hier_post &&
     ++	git checkout --track=fetch -b local_hier nested/remote/fetch_hier &&
     ++	test_cmp_rev refs/remotes/nested/remote/fetch_hier HEAD
     ++'
     ++
      +test_expect_success 'checkout --track=inherit,direct is rejected' '
      +	test_must_fail git checkout --track=inherit,direct -b bad fetch_upstream/fetch_new 2>err &&
      +	test_grep "cannot combine" err


 Documentation/git-checkout.adoc |  13 ++-
 Documentation/git-switch.adoc   |  13 ++-
 builtin/checkout.c              | 168 +++++++++++++++++++++++++++++++-
 t/t7201-co.sh                   | 144 +++++++++++++++++++++++++++
 4 files changed, 332 insertions(+), 6 deletions(-)

diff --git a/Documentation/git-checkout.adoc b/Documentation/git-checkout.adoc
index 43ccf47cf6..28f17f427e 100644
--- a/Documentation/git-checkout.adoc
+++ b/Documentation/git-checkout.adoc
@@ -158,11 +158,22 @@ of it").
 	resets _<branch>_ to the start point instead of failing.
 
 `-t`::
-`--track[=(direct|inherit)]`::
+`--track[=(direct|inherit|fetch)[,...]]`::
 	When creating a new branch, set up "upstream" configuration. See
 	`--track` in linkgit:git-branch[1] for details. As a convenience,
 	--track without -b implies branch creation.
 +
+The argument is a comma-separated list. `direct` (the default) and
+`inherit` select the tracking mode and are mutually exclusive. Adding
+`fetch` requests that the remote be fetched before _<start-point>_ is
+resolved, so the new branch starts from a fresh tip: when
+_<start-point>_ is in _<remote>/<branch>_ form, only that branch is
+updated; when _<start-point>_ is a bare remote name (e.g. `origin`),
+only the remote's default branch is updated. If the fetch fails and the
+corresponding remote-tracking ref already exists, a warning is printed
+and the checkout proceeds from the existing tip; otherwise the checkout
+is aborted.
++
 If no `-b` option is given, the name of the new branch will be
 derived from the remote-tracking branch, by looking at the local part of
 the refspec configured for the corresponding remote, and then stripping
diff --git a/Documentation/git-switch.adoc b/Documentation/git-switch.adoc
index 87707e9265..3f54cf39e9 100644
--- a/Documentation/git-switch.adoc
+++ b/Documentation/git-switch.adoc
@@ -154,11 +154,22 @@ should result in deletion of the path).
 	attached to a terminal, regardless of `--quiet`.
 
 `-t`::
-`--track[ (direct|inherit)]`::
+`--track[=(direct|inherit|fetch)[,...]]`::
 	When creating a new branch, set up "upstream" configuration.
 	`-c` is implied. See `--track` in linkgit:git-branch[1] for
 	details.
 +
+The argument is a comma-separated list. `direct` (the default) and
+`inherit` select the tracking mode and are mutually exclusive. Adding
+`fetch` requests that the remote be fetched before _<start-point>_ is
+resolved, so the new branch starts from a fresh tip: when
+_<start-point>_ is in _<remote>/<branch>_ form, only that branch is
+updated; when _<start-point>_ is a bare remote name (e.g. `origin`),
+only the remote's default branch is updated. If the fetch fails and the
+corresponding remote-tracking ref already exists, a warning is printed
+and the switch proceeds from the existing tip; otherwise the switch is
+aborted.
++
 If no `-c` option is given, the name of the new branch will be derived
 from the remote-tracking branch, by looking at the local part of the
 refspec configured for the corresponding remote, and then stripping
diff --git a/builtin/checkout.c b/builtin/checkout.c
index ac0186a33e..aff442c526 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -26,10 +26,12 @@
 #include "preload-index.h"
 #include "read-cache.h"
 #include "refs.h"
+#include "refspec.h"
 #include "remote.h"
 #include "repo-settings.h"
 #include "resolve-undo.h"
 #include "revision.h"
+#include "run-command.h"
 #include "setup.h"
 #include "strvec.h"
 #include "submodule.h"
@@ -62,6 +64,7 @@ struct checkout_opts {
 	int count_checkout_paths;
 	int overlay_mode;
 	int dwim_new_local_branch;
+	int fetch;
 	int discard_changes;
 	int accept_ref;
 	int accept_pathspec;
@@ -113,6 +116,158 @@ struct branch_info {
 	char *checkout;
 };
 
+static int resolve_fetch_target(const char *arg, char **remote_out,
+				char **src_ref_out, char **existing_ref_out)
+{
+	const char *slash;
+	char *remote_name = NULL;
+	struct remote *remote = NULL;
+	struct refspec_item query = { 0 };
+	struct strbuf dst = STRBUF_INIT;
+	struct object_id oid;
+	const char *rest = NULL;
+	const char *head_target = NULL;
+	const char *short_target;
+
+	*remote_out = NULL;
+	*src_ref_out = NULL;
+	*existing_ref_out = NULL;
+
+	if (!arg || !*arg || *arg == '/')
+		return -1;
+
+	slash = arg + strlen(arg);
+	while (1) {
+		free(remote_name);
+		remote_name = xstrndup(arg, slash - arg);
+		remote = remote_get(remote_name);
+		if (remote && remote_is_configured(remote, 1))
+			break;
+		while (slash > arg && *--slash != '/')
+			;
+		if (slash == arg) {
+			free(remote_name);
+			return -1;
+		}
+	}
+
+	if (*slash == '/' && slash[1])
+		rest = slash + 1;
+	if (!rest) {
+		strbuf_addf(&dst, "refs/remotes/%s/HEAD", remote_name);
+		head_target = refs_resolve_ref_unsafe(get_main_ref_store(the_repository),
+						      dst.buf,
+						      RESOLVE_REF_READING |
+						      RESOLVE_REF_NO_RECURSE,
+						      &oid, NULL);
+		if (head_target) {
+			*existing_ref_out = xstrdup(dst.buf);
+			if (skip_prefix(head_target, "refs/remotes/", &short_target) &&
+			    skip_prefix(short_target, remote_name, &short_target) &&
+			    *short_target == '/')
+				rest = short_target + 1;
+		}
+		strbuf_reset(&dst);
+	}
+
+	if (rest) {
+		strbuf_addf(&dst, "refs/remotes/%s/%s", remote_name, rest);
+		query.dst = dst.buf;
+		if (!remote_find_tracking(remote, &query) && query.src) {
+			*src_ref_out = xstrdup(query.src);
+			free(query.src);
+		} else {
+			*src_ref_out = xstrdup(rest);
+		}
+		if (!*existing_ref_out) {
+			strbuf_reset(&dst);
+			strbuf_addf(&dst, "refs/remotes/%s", arg);
+			if (!refs_read_ref(get_main_ref_store(the_repository),
+					   dst.buf, &oid))
+				*existing_ref_out = xstrdup(dst.buf);
+		}
+	}
+
+	strbuf_release(&dst);
+	*remote_out = remote_name;
+	return 0;
+}
+
+static void fetch_remote_for_start_point(const char *arg)
+{
+	char *remote_name = NULL;
+	char *src_ref = NULL;
+	char *existing_ref = NULL;
+	struct child_process cmd = CHILD_PROCESS_INIT;
+
+	if (resolve_fetch_target(arg, &remote_name, &src_ref, &existing_ref))
+		return;
+
+	strvec_pushl(&cmd.args, "fetch", remote_name, NULL);
+	if (src_ref)
+		strvec_push(&cmd.args, src_ref);
+	cmd.git_cmd = 1;
+	if (run_command(&cmd)) {
+		if (existing_ref)
+			warning(_("failed to fetch start-point '%s'; "
+				  "using existing '%s'"),
+				arg, existing_ref);
+		else
+			die(_("failed to fetch start-point '%s'"), arg);
+	}
+
+	free(remote_name);
+	free(src_ref);
+	free(existing_ref);
+}
+
+static int parse_opt_checkout_track(const struct option *opt,
+				    const char *arg, int unset)
+{
+	struct checkout_opts *opts = opt->value;
+	struct string_list tokens = STRING_LIST_INIT_DUP;
+	struct string_list_item *item;
+	int saw_direct = 0, saw_inherit = 0;
+	int ret = 0;
+
+	opts->fetch = 0;
+
+	if (unset) {
+		opts->track = BRANCH_TRACK_NEVER;
+		return 0;
+	}
+
+	opts->track = BRANCH_TRACK_EXPLICIT;
+	if (!arg)
+		return 0;
+
+	string_list_split(&tokens, arg, ",", -1);
+	for_each_string_list_item(item, &tokens) {
+		if (!strcmp(item->string, "fetch")) {
+			opts->fetch = 1;
+		} else if (!strcmp(item->string, "direct")) {
+			saw_direct = 1;
+			opts->track = BRANCH_TRACK_EXPLICIT;
+		} else if (!strcmp(item->string, "inherit")) {
+			saw_inherit = 1;
+			opts->track = BRANCH_TRACK_INHERIT;
+		} else {
+			ret = error(_("option `%s' expects \"%s\", \"%s\", "
+				      "or \"%s\""),
+				    "--track", "direct", "inherit", "fetch");
+			goto out;
+		}
+	}
+
+	if (saw_direct && saw_inherit)
+		ret = error(_("option `%s' cannot combine \"%s\" and \"%s\""),
+			    "--track", "direct", "inherit");
+
+out:
+	string_list_clear(&tokens, 0);
+	return ret;
+}
+
 static void branch_info_release(struct branch_info *info)
 {
 	free(info->name);
@@ -1741,10 +1896,10 @@ static struct option *add_common_switch_branch_options(
 {
 	struct option options[] = {
 		OPT_BOOL('d', "detach", &opts->force_detach, N_("detach HEAD at named commit")),
-		OPT_CALLBACK_F('t', "track",  &opts->track, "(direct|inherit)",
+		OPT_CALLBACK_F('t', "track",  opts, "(direct|inherit|fetch)[,...]",
 			N_("set branch tracking configuration"),
 			PARSE_OPT_OPTARG,
-			parse_opt_tracking_mode),
+			parse_opt_checkout_track),
 		OPT__FORCE(&opts->force, N_("force checkout (throw away local modifications)"),
 			   PARSE_OPT_NOCOMPLETE),
 		OPT_STRING(0, "orphan", &opts->new_orphan_branch, N_("new-branch"), N_("new unborn branch")),
@@ -1949,8 +2104,13 @@ static int checkout_main(int argc, const char **argv, const char *prefix,
 			opts->dwim_new_local_branch &&
 			opts->track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts->new_branch;
-		int n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
-					     &new_branch_info, opts, &rev);
+		int n;
+
+		if (opts->fetch)
+			fetch_remote_for_start_point(argv[0]);
+
+		n = parse_branchname_arg(argc, argv, dwim_ok, which_command,
+					 &new_branch_info, opts, &rev);
 		argv += n;
 		argc -= n;
 	} else if (!opts->accept_ref && opts->from_treeish) {
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 9bcf7c0b40..6dfe9ec931 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -801,4 +801,148 @@ test_expect_success 'tracking info copied with autoSetupMerge=inherit' '
 	test_cmp_config "" --default "" branch.main2.merge
 '
 
+test_expect_success 'setup upstream for --track=fetch tests' '
+	git checkout main &&
+	git init fetch_upstream &&
+	test_commit -C fetch_upstream u_main &&
+	git remote add fetch_upstream fetch_upstream &&
+	git fetch fetch_upstream &&
+	git -C fetch_upstream checkout -b fetch_new &&
+	test_commit -C fetch_upstream u_new
+'
+
+test_expect_success 'checkout --track=fetch -b picks up branch created upstream after clone' '
+	git checkout main &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_new &&
+	git checkout --track=fetch -b local_new fetch_upstream/fetch_new &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_new HEAD &&
+	test_cmp_config fetch_upstream branch.local_new.remote &&
+	test_cmp_config refs/heads/fetch_new branch.local_new.merge
+'
+
+test_expect_success 'checkout --track=fetch <remote>/<branch> leaves other tracking branches untouched' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_target &&
+	test_commit -C fetch_upstream u_target_pre &&
+	git -C fetch_upstream checkout -b fetch_other &&
+	test_commit -C fetch_upstream u_other_pre &&
+	git fetch fetch_upstream &&
+	other_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_other) &&
+	git -C fetch_upstream checkout fetch_target &&
+	test_commit -C fetch_upstream u_target_post &&
+	git -C fetch_upstream checkout fetch_other &&
+	test_commit -C fetch_upstream u_other_post &&
+	git checkout --track=fetch -b local_target fetch_upstream/fetch_target &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_target HEAD &&
+	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_other)" = "$other_before"
+'
+
+test_expect_success 'checkout --track=fetch with bare remote name fetches only <remote>/HEAD target' '
+	git checkout main &&
+	git -C fetch_upstream checkout main &&
+	git remote set-head fetch_upstream main &&
+	git -C fetch_upstream checkout -b fetch_unrelated &&
+	test_commit -C fetch_upstream u_unrelated_pre &&
+	git fetch fetch_upstream fetch_unrelated &&
+	unrelated_before=$(git rev-parse refs/remotes/fetch_upstream/fetch_unrelated) &&
+	git -C fetch_upstream checkout main &&
+	test_commit -C fetch_upstream u_main_post &&
+	git -C fetch_upstream checkout fetch_unrelated &&
+	test_commit -C fetch_upstream u_unrelated_post &&
+	git checkout --track=fetch -b local_from_remote fetch_upstream &&
+	test_cmp_rev refs/remotes/fetch_upstream/main HEAD &&
+	test "$(git rev-parse refs/remotes/fetch_upstream/fetch_unrelated)" = "$unrelated_before"
+'
+
+test_expect_success 'checkout --track=fetch aborts and does not create branch when no existing ref' '
+	git checkout main &&
+	test_might_fail git branch -D bogus &&
+	test_must_fail git checkout --track=fetch -b bogus fetch_upstream/does_not_exist &&
+	test_must_fail git rev-parse --verify refs/heads/bogus
+'
+
+test_expect_success 'checkout --track=fetch warns and proceeds when fetch fails but ref exists' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_offline &&
+	test_commit -C fetch_upstream u_offline &&
+	git fetch fetch_upstream fetch_offline &&
+	saved_url=$(git config remote.fetch_upstream.url) &&
+	test_when_finished "git config remote.fetch_upstream.url \"$saved_url\"" &&
+	git config remote.fetch_upstream.url ./does-not-exist &&
+	git checkout --track=fetch -b local_offline fetch_upstream/fetch_offline 2>err &&
+	test_grep "failed to fetch" err &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_offline HEAD
+'
+
+test_expect_success 'checkout --track=fetch resolves through configured fetch refspec' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_refspec &&
+	test_commit -C fetch_upstream u_refspec &&
+	git fetch fetch_upstream fetch_refspec &&
+	git remote add fetch_custom ./fetch_upstream &&
+	test_when_finished "git remote remove fetch_custom" &&
+	git config --replace-all remote.fetch_custom.fetch \
+		"+refs/heads/*:refs/remotes/custom-ns/*" &&
+	git fetch fetch_custom &&
+	test_commit -C fetch_upstream u_refspec_post &&
+	git checkout --track=fetch -b local_refspec custom-ns/fetch_refspec &&
+	test_cmp_rev refs/remotes/custom-ns/fetch_refspec HEAD
+'
+
+test_expect_success 'checkout --track=fetch handles hierarchical remote name' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_hier &&
+	test_commit -C fetch_upstream u_hier &&
+	git remote add nested/remote ./fetch_upstream &&
+	test_when_finished "git remote remove nested/remote" &&
+	git fetch nested/remote fetch_hier &&
+	test_commit -C fetch_upstream u_hier_post &&
+	git checkout --track=fetch -b local_hier nested/remote/fetch_hier &&
+	test_cmp_rev refs/remotes/nested/remote/fetch_hier HEAD
+'
+
+test_expect_success 'checkout --track=inherit,direct is rejected' '
+	test_must_fail git checkout --track=inherit,direct -b bad fetch_upstream/fetch_new 2>err &&
+	test_grep "cannot combine" err
+'
+
+test_expect_success 'checkout --track=fetch then --track=direct drops fetch (last-one-wins)' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_lastwin &&
+	test_commit -C fetch_upstream u_lastwin &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_lastwin &&
+	test_must_fail git checkout --track=fetch --track=direct \
+		-b local_lastwin fetch_upstream/fetch_lastwin &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_lastwin
+'
+
+test_expect_success 'checkout --track=fetch,inherit fetches and inherits' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_inherit &&
+	test_commit -C fetch_upstream u_inherit &&
+	git fetch fetch_upstream fetch_inherit &&
+	git checkout -b base_inherit fetch_upstream/fetch_inherit &&
+	test_commit -C fetch_upstream u_inherit2 &&
+	git checkout main &&
+	git checkout --track=fetch,inherit -b local_inherit base_inherit &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_inherit HEAD &&
+	test_cmp_config fetch_upstream branch.local_inherit.remote &&
+	test_cmp_config refs/heads/fetch_inherit branch.local_inherit.merge
+'
+
+test_expect_success 'checkout --track=bogus reports an error' '
+	git checkout main &&
+	test_must_fail git checkout --track=bogus -b bogus_branch fetch_upstream/fetch_new 2>err &&
+	test_grep "expects" err
+'
+
+test_expect_success 'switch --track=fetch -c picks up branch created upstream after clone' '
+	git checkout main &&
+	git -C fetch_upstream checkout -b fetch_switch &&
+	test_commit -C fetch_upstream u_switch &&
+	test_must_fail git rev-parse --verify refs/remotes/fetch_upstream/fetch_switch &&
+	git switch --track=fetch -c local_switch fetch_upstream/fetch_switch &&
+	test_cmp_rev refs/remotes/fetch_upstream/fetch_switch HEAD
+'
+
 test_done

base-commit: 29bd7ed5127255713c1ac2f43b7c6f257d7b4594
-- 
gitgitgadget

Re: [PATCH v14 5/5] checkout -m: autostash when switching branches

[Phillip Wood]

Hi Harald

On 15/04/2026 17:24, Harald Nordgren via GitGitGadget wrote:
(trimming the documentation - I'll try and look at that next time)

> diff --git a/builtin/checkout.c b/builtin/checkout.c
> index c80c62b37b..55c4db04c6 100644
> --- a/builtin/checkout.c
> +++ b/builtin/checkout.c
> @@ -17,7 +17,6 @@
>   #include "merge-ll.h"
>   #include "lockfile.h"
>   #include "mem-pool.h"
> -#include "merge-ort-wrappers.h"
>   #include "object-file.h"
>   #include "object-name.h"
>   #include "odb.h"
> @@ -30,6 +29,7 @@
>   #include "repo-settings.h"
>   #include "resolve-undo.h"
>   #include "revision.h"
> +#include "sequencer.h"
>   #include "setup.h"
>   #include "submodule.h"
>   #include "symlinks.h"
> @@ -853,90 +853,8 @@ static int merge_working_tree(const struct checkout_opts *opts,
>   		ret = unpack_trees(2, trees, &topts);
>   		clear_unpack_trees_porcelain(&topts);
>   		if (ret == -1) {
> -			/*
> -			 * Unpack couldn't do a trivial merge; either
> -			 * give up or do a real merge, depending on
> -			 * whether the merge flag was used.
> -			 */
> -			struct tree *work;
> -			struct tree *old_tree;
> -			struct merge_options o;
> -			struct strbuf sb = STRBUF_INIT;
> -			struct strbuf old_commit_shortname = STRBUF_INIT;
> -
> -			if (!opts->merge) {
> -				rollback_lock_file(&lock_file);
> -				return 1;
> -			}
> -
> -			/*
> -			 * Without old_branch_info->commit, the below is the same as
> -			 * the two-tree unpack we already tried and failed.
> -			 */
> -			if (!old_branch_info->commit) {
> -				rollback_lock_file(&lock_file);
> -				return 1;
> -			}
> -			old_tree = repo_get_commit_tree(the_repository,
> -							old_branch_info->commit);
> -
> -			if (repo_index_has_changes(the_repository, old_tree, &sb))
> -				die(_("cannot continue with staged changes in "
> -				      "the following files:\n%s"), sb.buf);
> -			strbuf_release(&sb);
> -
> -			/* Do more real merge */
> -
> -			/*
> -			 * We update the index fully, then write the
> -			 * tree from the index, then merge the new
> -			 * branch with the current tree, with the old
> -			 * branch as the base. Then we reset the index
> -			 * (but not the working tree) to the new
> -			 * branch, leaving the working tree as the
> -			 * merged version, but skipping unmerged
> -			 * entries in the index.
> -			 */
> -
> -			add_files_to_cache(the_repository, NULL, NULL, NULL, 0,
> -					0, 0);
> -			init_ui_merge_options(&o, the_repository);
> -			o.verbosity = 0;
> -			work = write_in_core_index_as_tree(the_repository,
> -							   the_repository->index);
> -
> -			ret = reset_tree(new_tree,
> -					 opts, 1,
> -					 writeout_error, new_branch_info);
> -			if (ret) {
> -				rollback_lock_file(&lock_file);
> -				return ret;
> -			}
> -			o.ancestor = old_branch_info->name;
> -			if (!old_branch_info->name) {
> -				strbuf_add_unique_abbrev(&old_commit_shortname,
> -							 &old_branch_info->commit->object.oid,
> -							 DEFAULT_ABBREV);
> -				o.ancestor = old_commit_shortname.buf;
> -			}
> -			o.branch1 = new_branch_info->name;
> -			o.branch2 = "local";
> -			o.conflict_style = opts->conflict_style;
> -			ret = merge_ort_nonrecursive(&o,
> -						     new_tree,
> -						     work,
> -						     old_tree);
> -			if (ret < 0)
> -				die(NULL);
> -			ret = reset_tree(new_tree,
> -					 opts, 0,
> -					 writeout_error, new_branch_info);
> -			strbuf_release(&o.obuf);
> -			strbuf_release(&old_commit_shortname);
> -			if (ret) {
> -				rollback_lock_file(&lock_file);
> -				return ret;
> -			}
> +			rollback_lock_file(&lock_file);
> +			return ret;

ret is -1 so we return the same value if unpack_trees() fails as do the 
checks at the top of the function do when they fail with "return 
error(...)". Therefore we cannot determine whether a failure of this 
function is due to unpack_trees() or not and so we wont know whether to 
autostash or not. You need to return a unique value here like -2 (or 
ideally a named constant)

>   		}
>   	}
>   
> @@ -1181,6 +1099,10 @@ static int switch_branches(const struct checkout_opts *opts,
>   	struct object_id rev;
>   	int flag, writeout_error = 0;
>   	int do_merge = 1;
> +	int created_autostash = 0;
> +	struct strbuf old_commit_shortname = STRBUF_INIT;
> +	struct strbuf autostash_msg = STRBUF_INIT;
> +	const char *stash_label_base = NULL;
>   
>   	trace2_cmd_mode("branch");
>   
> @@ -1218,11 +1140,39 @@ static int switch_branches(const struct checkout_opts *opts,
>   			do_merge = 0;
>   	}
>   
> +	if (old_branch_info.name)
> +		stash_label_base = old_branch_info.name;
> +	else if (old_branch_info.commit) {

Style: if one branch of an if statement has braces then all branch should.

> +		strbuf_add_unique_abbrev(&old_commit_shortname,
> +					 &old_branch_info.commit->object.oid,
> +					 DEFAULT_ABBREV);
> +		stash_label_base = old_commit_shortname.buf;
> +	}
> +
>   	if (do_merge) {
>   		ret = merge_working_tree(opts, &old_branch_info, new_branch_info, &writeout_error);
> +		if (ret == -1 && opts->merge) {
> +			strbuf_addf(&autostash_msg,
> +				    "autostash while switching to '%s'",
> +				    new_branch_info->name);
> +			create_autostash_ref(the_repository,
> +					     "CHECKOUT_AUTOSTASH_HEAD",
> +					     autostash_msg.buf, true);
> +			created_autostash = 1;
> +			ret = merge_working_tree(opts, &old_branch_info, new_branch_info, &writeout_error);
> +		}
>   		if (ret) {
> +			if (created_autostash)
> +				apply_autostash_ref(the_repository,
> +						    "CHECKOUT_AUTOSTASH_HEAD",
> +						    new_branch_info->name,
> +						    "local",
> +						    stash_label_base,
> +						    autostash_msg.buf);

Good - now we only try to restore the stashed changes if we actually 
stashed. However we only restore the stashed changes if there was an 
error(). If there isn't an error we call update_refs_for_switch() before 
restoring them. It would be safer to restore them straight away in case 
that function ends up dying for any reason (though I think that's pretty 
unlikely)

	if (created_autostash) {
		if (opts->conflict_style >= 0)
			/* set up confilct style */
		apply_autostash_ref(...);
	}
	if (ret) {

>   			branch_info_release(&old_branch_info);
> -			return ret;
> +			strbuf_release(&old_commit_shortname);
> +			strbuf_release(&autostash_msg);
> +			return ret < 0 ? 1 : ret;

This changes the return value for all errors from merge_working_tree() - 
that's probably a good this as this value is used for the exit code and 
we don't really want an exit code of -1

>   		}
>   	}
>   
> @@ -1231,8 +1181,30 @@ static int switch_branches(const struct checkout_opts *opts,
>   
>   	update_refs_for_switch(opts, &old_branch_info, new_branch_info);
>   
> +	if (opts->conflict_style >= 0) {
> +		struct strbuf cfg = STRBUF_INIT;
> +		strbuf_addf(&cfg, "merge.conflictStyle=%s",
> +			    conflict_style_name(opts->conflict_style));
> +		git_config_push_parameter(cfg.buf);
> +		strbuf_release(&cfg);
> +	}
> +	apply_autostash_ref(the_repository, "CHECKOUT_AUTOSTASH_HEAD",
> +			    new_branch_info->name, "local",
> +			    stash_label_base,
> +			    autostash_msg.buf);> +	discard_index(the_repository->index);

As I said last time we should not be calling apply_autostash() if we 
have not created an autostash. We should also not discard and re-read 
the index if we haven't stashed. I do think we'd be better restoring the 
stashed changes in a single place as I said above.

> +	if (repo_read_index(the_repository) < 0)
> +		die(_("index file corrupt"));
> +
> +	if (created_autostash && !opts->quiet && new_branch_info->commit)
> +		show_local_changes(&new_branch_info->commit->object,
> +				   &opts->diff_options);

This shows the local changes, but it doesn't give any explanation of 
what the output is. For example when switching branches with a conflict 
I see

Your local changes are stashed, however, applying it to carry
forward your local changes resulted in conflicts:

  - You can try resolving them now.  If you resolved them
    successfully, discard the stash entry with "git stash drop".

  - Alternatively you can "git reset --hard" if you do not want
    to deal with them right now, and later "git stash pop" to
    recover your local changes.
M	t/t7201-co.sh

where the changes appear to be part of the advice message. Perhaps we 
should print a short (i.e. one sentance) message along the lines of

	The following paths have local changes

We should test what the user sees here as well.

> +
>   	ret = post_checkout_hook(old_branch_info.commit, new_branch_info->commit, 1);
>   	branch_info_release(&old_branch_info);
> +	strbuf_release(&old_commit_shortname);
> +	strbuf_release(&autostash_msg);
>   
>   	return ret || writeout_error;
>   }
> diff --git a/sequencer.c b/sequencer.c
> index 7c0376d9e4..480e8e6c0b 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -4765,15 +4765,23 @@ static int apply_save_autostash_oid(const char *stash_oid, int attempt_apply,
>   		strvec_push(&store.args, stash_oid);
>   		if (run_command(&store))
>   			ret = error(_("cannot store %s"), stash_oid);
> +		else if (attempt_apply)
> +			fprintf(stderr,
> +				_("Your local changes are stashed, however, applying it to carry\n"
> +				  "forward your local changes resulted in conflicts:\n"

I'm not sure we need to say "local changes" twice here

	Your local changes are stashed, however applying them
	resulted in conflicts.

> +				  "\n"
> +				  " - You can try resolving them now.  If you resolved them\n"
> +				  "   successfully, discard the stash entry with \"git stash drop\".\n"

s/resolved/resolve/

> +				  "\n"
> +				  " - Alternatively you can \"git reset --hard\" if you do not want\n"
> +				  "   to deal with them right now, and later \"git stash pop\" to\n"
> +				  "   recover your local changes.\n"));

I find the bulleted list a bit odd, maybe

	You can either resolve the conflicts and then discard the stash
  	with "git stash drop", or, if you do not want to resolve them
	now, run "git reset --hard" and apply the local changes later by
	running "git stash pop"

would be better?

>   		else
>   			fprintf(stderr,
> -				_("%s\n"
> +				_("Autostash exists; creating a new stash entry.\n"
>   				  "Your changes are safe in the stash.\n"
>   				  "You can run \"git stash pop\" or"
> -				  " \"git stash drop\" at any time.\n"),
> -				attempt_apply ?
> -				_("Applying autostash resulted in conflicts.") :
> -				_("Autostash exists; creating a new stash entry."));
> +				  " \"git stash drop\" at any time.\n"));
>   	}
>   
>   	return ret;
> diff --git a/t/t3420-rebase-autostash.sh b/t/t3420-rebase-autostash.sh
> index ad3ba6a984..e4e2cb19ce 100755
> --- a/t/t3420-rebase-autostash.sh
> +++ b/t/t3420-rebase-autostash.sh
> @@ -61,18 +61,30 @@ create_expected_failure_apply () {
>   	First, rewinding head to replay your work on top of it...
>   	Applying: second commit
>   	Applying: third commit
> -	Applying autostash resulted in conflicts.
> -	Your changes are safe in the stash.
> -	You can run "git stash pop" or "git stash drop" at any time.
> +	Your local changes are stashed, however, applying it to carry
> +	forward your local changes resulted in conflicts:
> +
> +	 - You can try resolving them now.  If you resolved them
> +	   successfully, discard the stash entry with "git stash drop".
> +
> +	 - Alternatively you can "git reset --hard" if you do not want
> +	   to deal with them right now, and later "git stash pop" to
> +	   recover your local changes.
>   	EOF
>   }
>   
>   create_expected_failure_merge () {
>   	cat >expected <<-EOF
>   	$(grep "^Created autostash: [0-9a-f][0-9a-f]*\$" actual)
> -	Applying autostash resulted in conflicts.
> -	Your changes are safe in the stash.
> -	You can run "git stash pop" or "git stash drop" at any time.
> +	Your local changes are stashed, however, applying it to carry
> +	forward your local changes resulted in conflicts:
> +
> +	 - You can try resolving them now.  If you resolved them
> +	   successfully, discard the stash entry with "git stash drop".
> +
> +	 - Alternatively you can "git reset --hard" if you do not want
> +	   to deal with them right now, and later "git stash pop" to
> +	   recover your local changes.
>   	Successfully rebased and updated refs/heads/rebased-feature-branch.
>   	EOF
>   }
> diff --git a/t/t7201-co.sh b/t/t7201-co.sh
> index 9bcf7c0b40..c474c6759f 100755
> --- a/t/t7201-co.sh
> +++ b/t/t7201-co.sh
> @@ -210,6 +210,214 @@ test_expect_success 'checkout --merge --conflict=diff3 <branch>' '
>   	test_cmp expect two
>   '
>   
> +test_expect_success 'checkout --merge --conflict=zdiff3 <branch>' '
> +	git checkout -f main &&
> +	git reset --hard &&
> +	git clean -f &&
> +
> +	fill a b X d e >two &&
> +	git checkout --merge --conflict=zdiff3 simple &&

If I change "zdiff3" to "diff3" this test still passes which is 
disappointing. As the code that parses the conflict style is shared with 
other commands and we already have tests for --conflict=diff3 and 
--conflict=merge I'm not sure this test adds much.

> +
> +	cat <<-EOF >expect &&
> +	a
> +	<<<<<<< simple
> +	c
> +	||||||| main
> +	b
> +	c
> +	d
> +	=======
> +	b
> +	X
> +	d
> +	>>>>>>> local
> +	e
> +	EOF
> +	test_cmp expect two
> +'
> +
> +test_expect_success 'checkout -m respects merge.conflictStyle config' '

Looking at the existing tests, 'checkout with --merge, in diff3 -m 
style' and 'checkout --conflict=merge, overriding config' already test 
that we respect merge.conflictStyle and that --conflict overrides it so 
I don't see what new coverage this test adds.

> +	git checkout -f main &&
> +	git reset --hard &&
> +	git clean -f &&
> +
> +	test_config merge.conflictStyle diff3 &&
> +	fill b d >two &&
> +	git checkout -m simple &&
> +
> +	cat <<-EOF >expect &&
> +	<<<<<<< simple
> +	a
> +	c
> +	e
> +	||||||| main
> +	a
> +	b
> +	c
> +	d
> +	e
> +	=======
> +	b
> +	d
> +	>>>>>>> local
> +	EOF
> +	test_cmp expect two
> +'
> +
> +test_expect_success 'checkout -m skips stash when no conflict' '
> +	git checkout -f main &&
> +	git clean -f &&
> +
> +	fill 0 x y z >same &&
> +	git stash list >stash-before &&
> +	git checkout -m side >actual 2>&1 &&

file "same" is unchanged between branch "side" and "branch" main so we 
do not need to stash it.

> +	test_grep ! "Created autostash" actual &&
> +	git stash list >stash-after &&
> +	test_cmp stash-before stash-after &&
> +	fill 0 x y z >expect &&
> +	test_cmp expect same

Even if we created an autostash this test would not pick it up as the 
stash is not written to refs/stash unless there are merge conflicts and 
we don't print "Created autostash" even when we do create an autostash. 
The same is true for "checkout -m -b skips stash with dirty tree" below. 
I don't see how we can check that a stash was not created without using 
GIT_TRACE to see if we run "git stash". Even that is fragile as we might 
start stashing without forking a separate process in future.

> +'
> +
> +test_expect_success 'checkout -m skips stash with non-conflicting dirty index' '
> +	git checkout -f main &&
> +	git clean -f &&
> +
> +	fill 0 x y z >same &&
> +	git add same &&
> +	git checkout -m side >actual 2>&1 &&
> +	test_grep ! "Created autostash" actual &&
> +	fill 0 x y z >expect &&
> +	test_cmp expect same
> +'
> +
> +test_expect_success 'checkout -m stashes and applies on conflicting changes' '
> +	git checkout -f main &&
> +	git clean -f &&
> +
> +	fill 1 2 3 4 5 6 7 >one &&
> +	git checkout -m side >actual 2>&1 &&
> +	test_grep ! "Created autostash" actual &&
> +	test_grep "Applied autostash" actual &&
> +	fill 1 2 3 4 5 6 7 >expect &&
> +	test_cmp expect one
> +'

I don't think the two tests above add any extra coverage when we have 
the one below so they can be deleted. Our test suite is slow enough 
already - we only need one test to fail for any given issue.

> +test_expect_success 'checkout -m with mixed staged and unstaged changes' '
> +	git checkout -f main &&
> +	git clean -f &&
> +
> +	fill 0 x y z >same &&
> +	git add same &&
> +	fill 1 2 3 4 5 6 7 >one &&
> +	git checkout -m side >actual 2>&1 &&
> +	test_grep ! "Created autostash" actual &&
> +	test_grep "Applied autostash" actual &&
> +	fill 0 x y z >expect &&
> +	test_cmp expect same &&
> +	fill 1 2 3 4 5 6 7 >expect &&
> +	test_cmp expect one
> +'
> +
> +test_expect_success 'checkout -m stashes on truly conflicting changes' '

This use of conflicting is rather confusing - what's the difference 
between a conflicting change and a truly conflicting change?

I think a single test is sufficient to check that we create a valid 
stash entry

test_expect_success 'checkout -m stashes on truly conflicting changes' '
	git checkout -f main &&
	git clean -f &&

	fill 1 2 3 4 5 >one &&
	test_must_fail git checkout side 2>stderr &&
	test_grep "Your local changes" stderr &&
	git checkout -m side >actual 2>&1 &&
	test_grep ! "Created autostash" actual &&
	test_grep "resulted in conflicts" actual &&
	test_grep "git stash drop" actual &&
	test_grep "recover your local changes" actual &&
	git show --format=%B --diff-merges=1 refs/stash >actual &&
	sed /^index/d actual >actual.trimmed &&
	cat >expect <<-EOF &&
	On main: autostash while switching to ${SQ}side${SQ}
	diff --git a/one b/one
	--- a/one
	+++ b/one
	@@ -3,6 +3,3 @@
	 3
	 4
	 5
	-6
	-7
	-8
	EOF
	test_cmp expect actual.trimmed &&
'

Then we can delete from here to ...

> +	git checkout -f main &&
> +	git clean -f &&
> +
> +	fill 1 2 3 4 5 >one &&
> +	test_must_fail git checkout side 2>stderr &&
> +	test_grep "Your local changes" stderr &&
> +	git checkout -m side >actual 2>&1 &&
> +	test_grep ! "Created autostash" actual &&
> +	test_grep "resulted in conflicts" actual &&
> +	test_grep "git stash drop" actual &&
> +	git stash drop &&
> +	git reset --hard
> +'
> +
> +test_expect_success 'checkout -m produces usable stash on conflict' '
> +	git checkout -f main &&
> +	git clean -f &&
> +
> +	fill 1 2 3 4 5 >one &&
> +	git checkout -m side >actual 2>&1 &&
> +	test_grep "recover your local changes" actual &&
> +	git checkout -f main &&
> +	git stash pop &&
> +	fill 1 2 3 4 5 >expect &&
> +	test_cmp expect one
> +'
> +
> +test_expect_success 'checkout -m autostash message includes target branch' '
> +	git checkout -f main &&
> +	git clean -f &&
> +
> +	fill 1 2 3 4 5 >one &&
> +	git checkout -m side >actual 2>&1 &&
> +	git stash list >stash-list &&
> +	test_grep "autostash while switching to .side." stash-list &&
> +	git stash drop &&
> +	git checkout -f main &&
> +	git reset --hard
> +'
> +
> +test_expect_success 'checkout -m stashes on staged conflicting changes' '
> +	git checkout -f main &&
> +	git clean -f &&
> +
> +	fill 1 2 3 4 5 >one &&
> +	git add one &&
> +	git checkout -m side >actual 2>&1 &&
> +	test_grep ! "Created autostash" actual &&
> +	test_grep "resulted in conflicts" actual &&
> +	test_grep "git stash drop" actual &&
> +	git stash drop &&
> +	git reset --hard
> +'

... here


> +test_expect_success 'checkout -m applies stash cleanly with non-overlapping changes in same file' '

I've no idea what this is trying to do - it looks more like it is 
testing that "git stash" works rather than anything to do with "git 
checkout"

> +	git checkout -f main &&
> +	git reset --hard &&
> +	git clean -f &&
> +
> +	git checkout -b nonoverlap_base &&
> +	fill a b c d >file &&
> +	git add file &&
> +	git commit -m "add file" &&
> +
> +	git checkout -b nonoverlap_child &&
> +	fill a b c INSERTED d >file &&
> +	git commit -a -m "insert line near end of file" &&
> +
> +	fill DIRTY a b c INSERTED d >file &&
> +
> +	git stash list >stash-before &&
> +	git checkout -m nonoverlap_base 2>stderr &&
> +	test_grep "Applied autostash" stderr &&
> +	test_grep ! "resulted in conflicts" stderr &&
> +
> +	git stash list >stash-after &&
> +	test_cmp stash-before stash-after &&
> +
> +	fill DIRTY a b c d >expect &&
> +	test_cmp expect file &&
> +
> +	git checkout -f main &&
> +	git branch -D nonoverlap_base &&
> +	git branch -D nonoverlap_child
> +'
> +
> +test_expect_success 'checkout -m -b skips stash with dirty tree' '
> +	git checkout -f main &&
> +	git clean -f &&
> +
> +	fill 0 x y z >same &&
> +	git checkout -m -b newbranch >actual 2>&1 &&
> +	test_grep ! "Created autostash" actual &&
> +	fill 0 x y z >expect &&
> +	test_cmp expect same &&
> +	git checkout main &&
> +	git branch -D newbranch
> +'

As I said above I don't think this test is testing what it claims to.

I'd suggest adding the following test

test_expect_success 'checkout -m which would overwrite untracked file' '
	git checkout -f --detach main &&
	test_commit another-file &&
	git checkout HEAD^ &&
	>another-file.t &&
	test_must_fail git checkout -m @{-1} 2>err &&
	test_grep "another-file.t.*overwritten" err
'

which passes on master but fails with these patches applied. We need to 
make sure that we don't set "quiet" in unpack_tree_opts the second time 
we call merge_working_tree(). The test could be improved by adding some 
local changes.

This is looking better, but there are still a couple of problems that 
need addressing before it can be considered ready for merging.

Thanks

Phillip

>   test_expect_success 'switch to another branch while carrying a deletion' '
>   	git checkout -f main &&
>   	git reset --hard &&
> diff --git a/t/t7600-merge.sh b/t/t7600-merge.sh
> index 9838094b66..cbef8a534e 100755
> --- a/t/t7600-merge.sh
> +++ b/t/t7600-merge.sh
> @@ -914,7 +914,7 @@ test_expect_success 'merge with conflicted --autostash changes' '
>   	git diff >expect &&
>   	test_when_finished "test_might_fail git stash drop" &&
>   	git merge --autostash c3 2>err &&
> -	test_grep "Applying autostash resulted in conflicts." err &&
> +	test_grep "your local changes resulted in conflicts" err &&
>   	git show HEAD:file >merge-result &&
>   	test_cmp result.1-9 merge-result &&
>   	git stash show -p >actual &&
> diff --git a/xdiff-interface.c b/xdiff-interface.c
> index f043330f2a..5ee2b96d0a 100644
> --- a/xdiff-interface.c
> +++ b/xdiff-interface.c
> @@ -325,6 +325,18 @@ int parse_conflict_style_name(const char *value)
>   		return -1;
>   }
>   
> +const char *conflict_style_name(int style)
> +{
> +	switch (style) {
> +	case XDL_MERGE_DIFF3:
> +		return "diff3";
> +	case XDL_MERGE_ZEALOUS_DIFF3:
> +		return "zdiff3";
> +	default:
> +		return "merge";
> +	}
> +}
> +
>   int git_xmerge_style = -1;
>   
>   int git_xmerge_config(const char *var, const char *value,
> diff --git a/xdiff-interface.h b/xdiff-interface.h
> index fbc4ceec40..ce54e1c0e0 100644
> --- a/xdiff-interface.h
> +++ b/xdiff-interface.h
> @@ -55,6 +55,7 @@ void xdiff_set_find_func(xdemitconf_t *xecfg, const char *line, int cflags);
>   void xdiff_clear_find_func(xdemitconf_t *xecfg);
>   struct config_context;
>   int parse_conflict_style_name(const char *value);
> +const char *conflict_style_name(int style);
>   int git_xmerge_config(const char *var, const char *value,
>   		      const struct config_context *ctx, void *cb);
>   extern int git_xmerge_style;

Comments on Phillip's review

[Harald Nordgren]

> ret is -1 so we return the same value if unpack_trees() fails as do the
> checks at the top of the function do when they fail with "return
> error(...)". Therefore we cannot determine whether a failure of this
> function is due to unpack_trees() or not and so we wont know whether to
> autostash or not. You need to return a unique value here like -2 (or
> ideally a named constant)

👍

> Good - now we only try to restore the stashed changes if we actually
> stashed. However we only restore the stashed changes if there was an
> error(). If there isn't an error we call update_refs_for_switch() before
> restoring them. It would be safer to restore them straight away in case
> that function ends up dying for any reason (though I think that's pretty
> unlikely)

I hope I understand correctly, the code becomes easier this way, so that's
nice!

> As I said last time we should not be calling apply_autostash() if we
> have not created an autostash. We should also not discard and re-read
> the index if we haven't stashed. I do think we'd be better restoring the
> stashed changes in a single place as I said above.

Makes sense.

> where the changes appear to be part of the advice message. Perhaps we
> should print a short (i.e. one sentance) message along the lines of
> 
>         The following paths have local changes
> 
> We should test what the user sees here as well.

Add that message.

Do you mean to test the full output? I'm not against it at all, but that
seems to be going against the convention of the other tests in this file.
But it would be a more robust test.

> I'm not sure we need to say "local changes" twice here

👍

> I find the bulleted list a bit odd, maybe
> 
>         You can either resolve the conflicts and then discard the stash
>         with "git stash drop", or, if you do not want to resolve them
>         now, run "git reset --hard" and apply the local changes later by
>         running "git stash pop"
> 
> would be better?

Much cleaner, thanks!

> we already have tests for --conflict=diff3 and
> --conflict=merge I'm not sure this test adds much.

Deleted.

> > +
> > +     cat <<-EOF >expect &&
> > +     a
> > +     <<<<<<< simple
> > +     c
> > +     ||||||| main
> > +     b
> > +     c
> > +     d
> > +     =======
> > +     b
> > +     X
> > +     d
> > +     >>>>>>> local
> > +     e
> > +     EOF
> > +     test_cmp expect two
> > +'
> > +
> > +test_expect_success 'checkout -m respects merge.conflictStyle config' '
> 
> Looking at the existing tests, 'checkout with --merge, in diff3 -m
> style' and 'checkout --conflict=merge, overriding config' already test
> that we respect merge.conflictStyle and that --conflict overrides it so
> I don't see what new coverage this test adds.

Deleted.

> > +test_expect_success 'checkout -m skips stash when no conflict' '
> > +     git checkout -f main &&
> > +     git clean -f &&
> > +
> > +     fill 0 x y z >same &&
> > +     git stash list >stash-before &&
> > +     git checkout -m side >actual 2>&1 &&
> 
> file "same" is unchanged between branch "side" and "branch" main so we
> do not need to stash it.

Deleted.

> > +     test_grep ! "Created autostash" actual &&
> > +     git stash list >stash-after &&
> > +     test_cmp stash-before stash-after &&
> > +     fill 0 x y z >expect &&
> > +     test_cmp expect same
> 
> Even if we created an autostash this test would not pick it up as the
> stash is not written to refs/stash unless there are merge conflicts and
> we don't print "Created autostash" even when we do create an autostash.
> The same is true for "checkout -m -b skips stash with dirty tree" below.
> I don't see how we can check that a stash was not created without using
> GIT_TRACE to see if we run "git stash". Even that is fragile as we might
> start stashing without forking a separate process in future.

Deleted.

> I don't think the two tests above add any extra coverage when we have
> the one below so they can be deleted. Our test suite is slow enough
> already - we only need one test to fail for any given issue.

Deleted.

> > +test_expect_success 'checkout -m stashes on truly conflicting changes' '
> 
> This use of conflicting is rather confusing - what's the difference
> between a conflicting change and a truly conflicting change?
> 
> I think a single test is sufficient to check that we create a valid
> stash entry

Updated.

> test_expect_success 'checkout -m which would overwrite untracked file' '
>         git checkout -f --detach main &&
>         test_commit another-file &&
>         git checkout HEAD^ &&
>         >another-file.t &&
>         test_must_fail git checkout -m @{-1} 2>err &&
>         test_grep "another-file.t.*overwritten" err
> '
> 
> which passes on master but fails with these patches applied. We need to
> make sure that we don't set "quiet" in unpack_tree_opts the second time
> we call merge_working_tree(). The test could be improved by adding some
> local changes.

Tricky to get right, the test if very good to have! I rewrote the logic now
to make this test pass, I hope it looks better now.


Harald