Re: [PATCH 24/34] checkout: reject if the branch is already checked out elsewhere

[Duy Nguyen <pclouds@gmail.com>]

On Sun, Nov 30, 2014 at 12:18:40PM -0500, Mark Levedahl wrote:
> On 11/30/2014 03:24 AM, Nguyễn Thái Ngọc Duy wrote:
> > One branch obviously can't be checked out at two places (but detached
> > heads are ok). Give the user a choice in this case: --detach, -b
> > new-branch, switch branch in the other checkout first or simply 'cd'
> > and continue to work there.
> >
> 
> This seems too restrictive and is not "obvious" to me: I currently use 
> git-new-workdir to have multiple checkouts of the same branch, with no 
> ill effect. While those who do not understand what is going on 
> underneath might be confused by one checkout suddenly showing 
> uncommitted diffs, I don't accept that as a reason to outright prevent 
> such use. I suggest, at the very least, that this behavior be overridden 
> by a --force flag?

Prevention is a strong word. It's more about safety for the mere
mortals. It's certainly possible to do something like this patch
(--force can't be reused, it already carries some other meaning).
Should I add this one in the next (hic) reroll?

-- 8< --
Subject: [PATCH] checkout: add --ignore-other-wortrees

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/git-checkout.txt |  6 ++++++
 builtin/checkout.c             | 19 +++++++++++--------
 t/t2025-checkout-to.sh         |  7 +++++++
 3 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt
index 0c13825..71d9e4e 100644
--- a/Documentation/git-checkout.txt
+++ b/Documentation/git-checkout.txt
@@ -232,6 +232,12 @@ section of linkgit:git-add[1] to learn how to operate the `--patch` mode.
 	specific files such as HEAD, index... See "MULTIPLE WORKING
 	TREES" section for more information.
 
+--ignore-other-worktrees::
+	`git checkout` refuses when the wanted ref is already checked out
+	by another worktree. This option makes it check the
+	ref out anyway. In other words, the ref is held by more than one
+	worktree.
+
 <branch>::
 	Branch to checkout; if it refers to a branch (i.e., a name that,
 	when prepended with "refs/heads/", is a valid ref), then that
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 953b763..8b2bf20 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -37,6 +37,7 @@ struct checkout_opts {
 	int writeout_stage;
 	int overwrite_ignore;
 	int ignore_skipworktree;
+	int ignore_other_worktrees;
 
 	const char *new_branch;
 	const char *new_branch_force;
@@ -1079,11 +1080,12 @@ static void check_linked_checkouts(struct branch_info *new)
 static int parse_branchname_arg(int argc, const char **argv,
 				int dwim_new_local_branch_ok,
 				struct branch_info *new,
-				struct tree **source_tree,
-				unsigned char rev[20],
-				const char **new_branch,
-				int force_detach)
+				struct checkout_opts *opts,
+				unsigned char rev[20])
 {
+	struct tree **source_tree = &opts->source_tree;
+	const char **new_branch = &opts->new_branch;
+	int force_detach = opts->force_detach;
 	int argcount = 0;
 	unsigned char branch_rev[20];
 	const char *arg;
@@ -1209,7 +1211,8 @@ static int parse_branchname_arg(int argc, const char **argv,
 		int flag;
 		char *head_ref = resolve_refdup("HEAD", 0, sha1, &flag);
 		if (head_ref &&
-		    (!(flag & REF_ISSYMREF) || strcmp(head_ref, new->path)))
+		    (!(flag & REF_ISSYMREF) || strcmp(head_ref, new->path)) &&
+		    !opts->ignore_other_worktrees)
 			check_linked_checkouts(new);
 		free(head_ref);
 	}
@@ -1340,6 +1343,8 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 				N_("second guess 'git checkout no-such-branch'")),
 		OPT_FILENAME(0, "to", &opts.new_worktree,
 			   N_("check a branch out in a separate working directory")),
+		OPT_BOOL(0, "ignore-other-worktrees", &opts.ignore_other_worktrees,
+			 N_("do not check if another worktree is holding the given ref")),
 		OPT_END(),
 	};
 
@@ -1420,9 +1425,7 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 			opts.track == BRANCH_TRACK_UNSPECIFIED &&
 			!opts.new_branch;
 		int n = parse_branchname_arg(argc, argv, dwim_ok,
-					     &new, &opts.source_tree,
-					     rev, &opts.new_branch,
-					     opts.force_detach);
+					     &new, &opts, rev);
 		argv += n;
 		argc -= n;
 	}
diff --git a/t/t2025-checkout-to.sh b/t/t2025-checkout-to.sh
index 915b506..f8e4df4 100755
--- a/t/t2025-checkout-to.sh
+++ b/t/t2025-checkout-to.sh
@@ -79,6 +79,13 @@ test_expect_success 'die the same branch is already checked out' '
 	)
 '
 
+test_expect_success 'not die the same branch is already checked out' '
+	(
+		cd here &&
+		git checkout --ignore-other-worktrees --to anothernewmaster newmaster
+	)
+'
+
 test_expect_success 'not die on re-checking out current branch' '
 	(
 		cd there &&
-- 
2.2.0.60.gb7b3c64

-- 8< --