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* [PATCH v3 2/3] MyFirstContribution: recommend the use of b4
From: Patrick Steinhardt @ 2026-06-08  6:49 UTC (permalink / raw)
  To: git
  Cc: Junio C Hamano, Tuomas Ahola, Weijie Yuan, Ramsay Jones,
	SZEDER Gábor, Kristoffer Haugsbakk, Toon Claes
In-Reply-To: <20260608-pks-b4-v3-0-f5e497d10c56@pks.im>

The b4 tool originates from the Linux kernel community and is intended
to help mailing-list based workflows. It automates a lot of the annoying
bookkeeping tasks that contributors typically need to do: tracking the
list of recipients, Message-IDs, range-diffs and the like. In addition
to that, b4 also has many other subcommands that help the maintainer and
reviewers.

The Git project uses the same infrastructure as the kernel, so this tool
is also a very good fit for us. Adapt "MyFirstContribution" to
explicitly recommend its use.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 Documentation/MyFirstContribution.adoc | 92 ++++++++++++++++++++++++++++++++--
 Documentation/SubmittingPatches        |  6 ++-
 2 files changed, 93 insertions(+), 5 deletions(-)

diff --git a/Documentation/MyFirstContribution.adoc b/Documentation/MyFirstContribution.adoc
index 984b7f5aa8..607876f3d8 100644
--- a/Documentation/MyFirstContribution.adoc
+++ b/Documentation/MyFirstContribution.adoc
@@ -833,7 +833,7 @@ This patchset is part of the MyFirstContribution tutorial and should not
 be merged.
 ----
 
-At this point the tutorial diverges, in order to demonstrate two
+At this point the tutorial diverges, in order to demonstrate three
 different methods of formatting your patchset and getting it reviewed.
 
 The first method to be covered is GitGitGadget, which is useful for those
@@ -845,9 +845,14 @@ more fine-grained control over the emails to be sent. This method requires some
 setup which can change depending on your system and will not be covered in this
 tutorial.
 
+The third method to be covered is `b4`, which builds on top of `git
+format-patch` and `git send-email`. This method is the recommended way to
+submit patches via mail as it automates a lot of the bookkeeping required by
+`git send-email`.
+
 Regardless of which method you choose, your engagement with reviewers will be
-the same; the review process will be covered after the sections on GitGitGadget
-and `git send-email`.
+the same; the review process will be covered after the sections on GitGitGadget,
+`git send-email` and `b4`.
 
 [[howto-ggg]]
 == Sending Patches via GitGitGadget
@@ -1296,6 +1301,87 @@ index 88f126184c..38da593a60 100644
 2.21.0.392.gf8f6787159e-goog
 ----
 
+[[howto-b4]]
+== Sending Patches with `b4`
+
+`b4` is a tool that builds on top of `git format-patch` and `git send-email`.
+It automates much of the bookkeeping involved in sending a patch series to a
+mailing-list-based project.
+
+Refer to the https://b4.docs.kernel.org/[b4 documentation] for a full reference.
+
+[[prep-b4]]
+=== Preparing a Patch Series
+
+`b4` tracks your patch series as a branch. To start tracking the `psuh` branch
+you have been working on, run:
+
+----
+$ b4 prep --enroll master
+----
+
+This enrolls the current branch, using `master` as the base of the topic. `b4`
+manages the cover letter as part of the branch, so you can edit it at any time
+with:
+
+----
+$ b4 prep --edit-cover
+----
+
+The cover letter not only tracks the content of the top-level mail, but also
+the set of recipients. You can add recipients by adding `To:` and `Cc:`
+trailer lines.
+
+[[send-b4]]
+=== Sending the Patches
+
+Before sending the series out for real, you can inspect what `b4` would send by
+passing `--dry-run`:
+
+----
+$ b4 send --dry-run
+----
+
+Once you are happy with the result, send the series with:
+
+----
+$ b4 send
+----
+
+[[v2-b4]]
+=== Sending v2
+
+When you are ready to send a new iteration of your series, refine your
+patches as usual using linkgit:git-rebase[1]. Note that you typically want to
+rebase on top of the cover letter. You can configure an alias to enable easy
+rebases going forward:
+
+---
+$ git config set alias.b4-rebase 'rebase "HEAD^{/--- b4-submit-tracking ---}"'
+$ git b4-rebase -i
+---
+
+Before sending out the new version you should also update the cover letter with
+`b4 prep --edit-cover` to note the relevant changes compared to the previous
+version. You can inspect the changes between the two versions with `b4 prep
+--compare-to=v1`.
+
+Same as with the first version, you can use `b4 send` to send out the second
+version. `b4` automatically bumps the version to `v2`, generates the range-diff
+against the previous iteration, and threads the new series as a reply to the
+cover letter of the first version.
+
+[[configure-b4]]
+=== Configure b4
+
+`b4` can be configured via linkgit:git-config[1]. In addition to that, projects
+can have their own set of defaults in `.b4-config` in the root tree, which also
+uses Git's config format. The user's configuration always takes precedence over
+the per-project defaults.
+
+Refer to the https://b4.docs.kernel.org/en/latest/config.html[b4 config documentation]
+for more information on the available options.
+
 [[now-what]]
 == My Patch Got Emailed - Now What?
 
diff --git a/Documentation/SubmittingPatches b/Documentation/SubmittingPatches
index d570184ec8..99427e1ee1 100644
--- a/Documentation/SubmittingPatches
+++ b/Documentation/SubmittingPatches
@@ -573,8 +573,10 @@ your existing e-mail client (often optimized for "multipart/*" MIME
 type e-mails) might render your patches unusable.
 
 NOTE: Here we outline the procedure using `format-patch` and
-`send-email`, but you can instead use GitGitGadget to send in your
-patches (see link:MyFirstContribution.html[MyFirstContribution]).
+`send-email`, but you can instead use GitGitGadget or `b4` to send in
+your patches (see link:MyFirstContribution.html[MyFirstContribution]).
+Contributors are encouraged to use `b4`, which automates much of the
+bookkeeping that is otherwise done by hand.
 
 People on the Git mailing list need to be able to read and
 comment on the changes you are submitting.  It is important for

-- 
2.54.0.1136.gdb2ca164c4.dirty


^ permalink raw reply related

* [PATCH v3 3/3] b4: introduce configuration for the Git project
From: Patrick Steinhardt @ 2026-06-08  6:49 UTC (permalink / raw)
  To: git
  Cc: Junio C Hamano, Tuomas Ahola, Weijie Yuan, Ramsay Jones,
	SZEDER Gábor, Kristoffer Haugsbakk, Toon Claes
In-Reply-To: <20260608-pks-b4-v3-0-f5e497d10c56@pks.im>

We're about to extend our documentation to recommend b4 for sending
patch series to the mailing list. Prepare for this by introducing a b4
configuration so that the tool knows to honor our preferences. For now,
this configuration does two things:

  - It configures "send-same-thread = shallow", which tells b4 to always
    send subsequent versions of the same patch series as a reply to the
    cover letter of the first version.

  - It configures "prep-cover-template", which tells b4 to use a custom
    template for the cover letter. The most important change compared to
    the default template is that our custom template also includes a
    range-diff.

There's potentially more things that we may want to configure going
forward, like for example auto-configuration of folks to Cc on certain
patches. But these two tweaks feel like a good place to start.

Note that these values only serve as defaults, and users may want to
tweak those defaults based on their own preference. Luckily, users can
do that without having to touch `.b4-config` at all, as b4 allows them
to override values via Git configuration:

    ```
    $ git config set b4.prep-cover-template /does/not/exist
    $ b4 send --dry-run
    ERROR: prep-cover-template says to use x, but it does not exist
    ```

So this gives users an easy way to override our defaults without having
to touch ".b4-config", which would dirty the tree.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 .b4-config         |  6 ++++++
 .b4-cover-template | 11 +++++++++++
 2 files changed, 17 insertions(+)

diff --git a/.b4-config b/.b4-config
new file mode 100644
index 0000000000..fd4fb56b6d
--- /dev/null
+++ b/.b4-config
@@ -0,0 +1,6 @@
+# Note that these are default values that you can tweak via the typical
+# git-config(1) machinery. You thus shouldn't ever have to change this file.
+# See also https://b4.docs.kernel.org/en/latest/config.html.
+[b4]
+send-same-thread = shallow
+prep-cover-template = ./.b4-cover-template
diff --git a/.b4-cover-template b/.b4-cover-template
new file mode 100644
index 0000000000..ab864933b5
--- /dev/null
+++ b/.b4-cover-template
@@ -0,0 +1,11 @@
+${cover}
+
+---
+${shortlog}
+
+${diffstat}
+
+${range_diff}
+---
+base-commit: ${base_commit}
+${prerequisites}

-- 
2.54.0.1136.gdb2ca164c4.dirty


^ permalink raw reply related

* Re: [PATCH] describe: limit default ref iteration to tags
From: Patrick Steinhardt @ 2026-06-08  6:59 UTC (permalink / raw)
  To: Tamir Duberstein; +Cc: git, Shawn O. Pearce, Junio C Hamano, Jeff King
In-Reply-To: <20260607-describe-tag-ref-scope-v1-1-653d232b86b5@gmail.com>

On Sun, Jun 07, 2026 at 04:51:53PM -0400, Tamir Duberstein wrote:
> Unless --all is given, get_name() rejects every ref outside refs/tags/.
> The rejection happens only after the ref backend has enumerated the ref,
> so repositories with many other refs spend most of a simple describe
> invocation visiting refs which cannot affect its result.

Right. The relevant block is this one:

	if (skip_prefix(ref->name, "refs/tags/", &path_to_match)) {
		is_tag = 1;
	} else if (all) {
		if ((exclude_patterns.nr || patterns.nr) &&
		    !skip_prefix(ref->name, "refs/heads/", &path_to_match) &&
		    !skip_prefix(ref->name, "refs/remotes/", &path_to_match)) {
			/* Only accept reference of known type if there are match/exclude patterns */
			return 0;
		}
	} else {
		/* Reject anything outside refs/tags/ unless --all */
		return 0;
	}

So we really only use tags unless "--all" is given.

> Commit 8a5a1884e9 (Avoid accessing non-tag refs in git-describe unless
> --all is requested, 2008-02-24) moved this rejection before object
> lookup, but left iteration unscoped. Pass the existing refs/tags/
> restriction to the iterator unless --all is given so the backend can
> avoid unrelated refs.
> 
> On a checkout with 124,357 refs, of which 330 were tags, I ran the
> following command with the parent and patched binaries:
> 
>     hyperfine --warmup 3 --runs 15 \
>         'git describe --always --long --abbrev=40 HEAD'
> 
> The results were:
> 
>              parent       this commit
>   elapsed    196.2 ms      63.3 ms
>   user        69.5 ms      48.0 ms
>   system     123.0 ms      12.0 ms

It's a bit curious that you don't post the hyperfine(1) results as-is
here.

> The wall-time standard deviations were 13.2 ms and 2.6 ms, respectively,
> for a 3.10x speedup.

Makes sense that this would result in a sizeable speedup, depending of
course on the shape of the existing refs in the repository.

> diff --git a/builtin/describe.c b/builtin/describe.c
> index 1c47d7c0b7..3532c8ff22 100644
> --- a/builtin/describe.c
> +++ b/builtin/describe.c
> @@ -740,6 +740,9 @@ int cmd_describe(int argc,
>  		return ret;
>  	}
>  
> +	if (!all)
> +		for_each_ref_opts.prefix = "refs/tags/";
> +
>  	hashmap_init(&names, commit_name_neq, NULL, 0);
>  	refs_for_each_ref_ext(get_main_ref_store(the_repository),
>  			      get_name, NULL, &for_each_ref_opts);

Another performance optimization that we could do here is to wire up the
exclude patterns via `for_each_ref_opts.exclude_patterns`. But that's
outside the scope of this patch series, and also much less likely to
help many use cases out there.

> diff --git a/t/perf/p6100-describe.sh b/t/perf/p6100-describe.sh
> index 069f91ce49..dfcaf59e90 100755
> --- a/t/perf/p6100-describe.sh
> +++ b/t/perf/p6100-describe.sh
> @@ -5,6 +5,12 @@ test_description='performance of git-describe'
>  
>  test_perf_default_repo
>  
> +test_lazy_prereq PERF_REFFILES '
> +	test "$(git rev-parse --show-ref-format)" = files
> +'
> +
> +ref_count=10000

Let's not declare this variable outside of tests.

> @@ -27,4 +33,18 @@ test_perf 'describe HEAD with one tag' '
>  	git describe --match=new HEAD
>  '
>  
> +test_expect_success PERF_REFFILES 'set up many unrelated refs' '
> +	git tag -m tip tip HEAD &&
> +	for i in $(test_seq $ref_count)
> +	do
> +		printf "create refs/heads/describe-perf/%05d HEAD\n" $i ||
> +		return 1
> +	done >instructions &&
> +	git update-ref --stdin <instructions
> +'

Why is this limited to the "files" backend, only? The logic should work
for both backends as-is.

Thanks!

Patrick

^ permalink raw reply

* Re: [PATCH] doc: fix typo in GIT_ALTERNATE_OBJECT_DIRECTORIES
From: Patrick Steinhardt @ 2026-06-08  7:02 UTC (permalink / raw)
  To: Alexander Monakov; +Cc: git
In-Reply-To: <20260605172643.8796-1-amonakov@ispras.ru>

On Fri, Jun 05, 2026 at 08:26:43PM +0300, Alexander Monakov wrote:
> One file accidentally spelled GIT_ALTERNATE_OBJECT_DIRECTORIES with
> REPOSITORIES instead of DIRECTORIES. Fix the typo.
> 
> Signed-off-by: Alexander Monakov <amonakov@ispras.ru>
> ---
>  Documentation/technical/hash-function-transition.adoc | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/Documentation/technical/hash-function-transition.adoc b/Documentation/technical/hash-function-transition.adoc
> index 2359d7d106..241d2f763d 100644
> --- a/Documentation/technical/hash-function-transition.adoc
> +++ b/Documentation/technical/hash-function-transition.adoc
> @@ -545,7 +545,7 @@ Alternates
>  ~~~~~~~~~~
>  For the same reason, a SHA-256 repository cannot borrow objects from a
>  SHA-1 repository using objects/info/alternates or
> -$GIT_ALTERNATE_OBJECT_REPOSITORIES.
> +$GIT_ALTERNATE_OBJECT_DIRECTORIES.

Yup, this change looks obviously good to me. Thanks!

Patrick

^ permalink raw reply

* Re: [PATCH v2 1/3] Documentation/MyFirstContribution: recommend shallow threading
From: Weijie Yuan @ 2026-06-08  8:31 UTC (permalink / raw)
  To: Patrick Steinhardt; +Cc: git, Junio C Hamano, Tuomas Ahola, Ramsay Jones
In-Reply-To: <aiZlu36Fh020L1Ip@pks.im>

On Mon, Jun 08, 2026 at 08:48:27AM +0200, Patrick Steinhardt wrote:
> On Wed, Jun 03, 2026 at 06:29:32PM +0800, Weijie Yuan wrote:
> > I'm afraid there will be some chaos.
> 
> I think "chaos" is a bit exaggerated.

Oops, sorry for my poor English, I guess "messy" would be a more proper
choice here? ;-)

> > As mentioned earlier, GitGitGadget now supports deep nesting of
> > iterations, if b4 changes while GitGitGadget doesn't, it would be
> > inconsistent in the archive. So, negotiation is necessary here.
> 
> That's a good point though -- if we change the recommendation, we should
> aim to change it consistently. I'll talk with Dscho (maintainer of GGG)
> today.

Thanks for your effort on this! Let´s see if the community can get on
the same page about this.

Thanks!

^ permalink raw reply

* Re: [PATCH v2 5/9] reset: introduce ability to skip reference updates
From: Patrick Steinhardt @ 2026-06-08  9:14 UTC (permalink / raw)
  To: phillip.wood; +Cc: git, Pablo Sabater, Junio C Hamano
In-Reply-To: <0fdaeec8-99cd-4dc9-9549-8a08133deebf@gmail.com>

On Fri, Jun 05, 2026 at 04:12:42PM +0100, Phillip Wood wrote:
> Hi Patrick
> 
> On 03/06/2026 17:14, Patrick Steinhardt wrote:
> > In a subsequent commit we'll introduce a new caller to `reset_head()`
> > that really only wants to update the index and working tree, without
> > updating any references. Introduce a new flag that lets the caller
> > perform this operation.
> 
> We already have a flag to update ORIG_HEAD so would it make more sense to
> have a flag to update HEAD, rather than adding a flag to disable the
> updates? It would mean updating the existing callers but I think it is a
> clearer api and it avoids the pitfall of
> 
> 	RESET_HEAD_ORIG_HEAD | RESET_HEAD_SKIP_REF_UPDATES

Hm. The question is whether it's sensible to have
`!RESET_HEAD_UPDATE_HEAD && RESET_HEAD_UPDATE_ORIG_HEAD`. That feels
like a somewhat weird request, too, and we'd have to introduce extra
logic to make that combination work.

> I wonder about the function name as well if we make updating HEAD optional
> then what does reset_head() mean? Maybe we should rename it something along
> the lines of reset_worktree() or update_working_copy()? I'm not really sure
> what a good name would be.

That's a good point, the name does get somewhat awkward. I think we
should keep "reset" in there, but `reset_worktree()` to me reads as it
if was rather related to git-worktree(1) than anything else. Maybe
`reset_working_tree()`?

Patrick

^ permalink raw reply

* Re: [PATCH v2 3/9] reset: modernize flags passed to `reset_head()`
From: Patrick Steinhardt @ 2026-06-08  9:14 UTC (permalink / raw)
  To: phillip.wood; +Cc: git, Pablo Sabater, Junio C Hamano
In-Reply-To: <9e2cb34b-97f6-44f4-be44-60f44760e601@gmail.com>

On Fri, Jun 05, 2026 at 04:08:57PM +0100, Phillip Wood wrote:
> Hi Patrick
> 
> On 03/06/2026 17:14, Patrick Steinhardt wrote:
> 
> > -/* Update ORIG_HEAD as well as HEAD */
> > -#define RESET_ORIG_HEAD (1<<4)
> > [...]> +	/* Update ORIG_HEAD as well as HEAD */
> > +	RESET_HEAD_ORIG_HEAD = (1 << 4),
> 
> I'm having a hard time parsing this new name, if we must have a
> "RESET_HEAD_" prefix can we call it something like
> RESET_HEAD_UPDATE_ORIG_HEAD?

Yeah, that reads better indeed. Amended locally, thanks!

Patrick

^ permalink raw reply

* Re: [PATCH v2 5/9] reset: introduce ability to skip reference updates
From: Patrick Steinhardt @ 2026-06-08  9:18 UTC (permalink / raw)
  To: phillip.wood; +Cc: git, Pablo Sabater, Junio C Hamano
In-Reply-To: <aiaH3ZmFZfmWYwr7@pks.im>

On Mon, Jun 08, 2026 at 11:14:08AM +0200, Patrick Steinhardt wrote:
> On Fri, Jun 05, 2026 at 04:12:42PM +0100, Phillip Wood wrote:
> > Hi Patrick
> > 
> > On 03/06/2026 17:14, Patrick Steinhardt wrote:
> > > In a subsequent commit we'll introduce a new caller to `reset_head()`
> > > that really only wants to update the index and working tree, without
> > > updating any references. Introduce a new flag that lets the caller
> > > perform this operation.
> > 
> > We already have a flag to update ORIG_HEAD so would it make more sense to
> > have a flag to update HEAD, rather than adding a flag to disable the
> > updates? It would mean updating the existing callers but I think it is a
> > clearer api and it avoids the pitfall of
> > 
> > 	RESET_HEAD_ORIG_HEAD | RESET_HEAD_SKIP_REF_UPDATES
> 
> Hm. The question is whether it's sensible to have
> `!RESET_HEAD_UPDATE_HEAD && RESET_HEAD_UPDATE_ORIG_HEAD`. That feels
> like a somewhat weird request, too, and we'd have to introduce extra
> logic to make that combination work.
> 
> > I wonder about the function name as well if we make updating HEAD optional
> > then what does reset_head() mean? Maybe we should rename it something along
> > the lines of reset_worktree() or update_working_copy()? I'm not really sure
> > what a good name would be.
> 
> That's a good point, the name does get somewhat awkward. I think we
> should keep "reset" in there, but `reset_worktree()` to me reads as it
> if was rather related to git-worktree(1) than anything else. Maybe
> `reset_working_tree()`?

I think I'll skip these changes for the next iteration for now. The
patch series has already exploded quite a bit in its scope due to the
refactorings of `reset_head()`, so I'd prefer to maybe do such changes
as a follow up.

Let me know in case you feel strongly about this though. Thanks!

Patrick

^ permalink raw reply

* Re: [PATCH RFC 1/2] builtin/history: abort reword on unchanged message
From: Patrick Steinhardt @ 2026-06-08  9:30 UTC (permalink / raw)
  To: Pablo Sabater; +Cc: git, Kaartic Sivaraam
In-Reply-To: <20260607-ps-history-reword-v1-1-ba43a3cbb81b@gmail.com>

On Sun, Jun 07, 2026 at 10:07:20PM +0200, Pablo Sabater wrote:
> When using `git history reword` if the new message is the same as the
> original it continues anyway creating a new commit with the same
> message and updates its descendants, modifying the history after this
> 'reworded' commit even though there was no actual change.
> 
> `git commit --amend` and `git rebase -i` + reword share this behavior,
> however `git history reword` is different:
> 1. Works in-memory without touching the index or the worktree [1], so
>    there are no side effects like staged files that could justify
>    rewriting the history when the commit message is the same.
> 2. `git history` by default updates all the branches [2] that contain the
>    original commit making it more costly than `git rebase -i` that only
>    updates the current branch.
> 
> Add a check if the original commit message is the same as the new one
> and abort if so.
> 
> [1]: https://lore.kernel.org/git/20260113-b4-pks-history-builtin-v11-8-e74ebfa2652d@pks.im/
> [2]: https://git-scm.com/docs/git-history#_description

Nit: I feel like both of the links don't really add much value.

> Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
> ---
>  builtin/history.c         | 10 ++++++++++
>  t/t3451-history-reword.sh | 20 ++++++++++++++++++++
>  2 files changed, 30 insertions(+)
> 
> diff --git a/builtin/history.c b/builtin/history.c
> index 0fc06fb204..51a22a9a1c 100644
> --- a/builtin/history.c
> +++ b/builtin/history.c
> @@ -135,6 +135,13 @@ static int commit_tree_ext(struct repository *repo,
>  					  original_body, action, &commit_message);
>  		if (ret < 0)
>  			goto out;
> +
> +		if (!strcmp(original_body, commit_message.buf)) {
> +			fprintf(stderr, _("Message unchanged,"
> +					  " aborting reword.\n"));
> +			ret = 1;
> +			goto out;
> +		}
>  	} else {
>  		strbuf_addstr(&commit_message, original_body);
>  	}

We also execute this logic via "git history fixup --reedit-message", and
here it wouldn't make sense to abort the commit in case the message is
unchanged.

Patrick

^ permalink raw reply

* Re: [PATCH RFC 2/2] builtin/history: print feedback after successful reword
From: Patrick Steinhardt @ 2026-06-08  9:30 UTC (permalink / raw)
  To: Pablo Sabater; +Cc: git, Kaartic Sivaraam
In-Reply-To: <20260607-ps-history-reword-v1-2-ba43a3cbb81b@gmail.com>

On Sun, Jun 07, 2026 at 10:07:21PM +0200, Pablo Sabater wrote:
> Unlike `git commit --amend` and `git rebase -i`, `git history reword`
> doesn't print anything, this makes it feel empty for a porcelain command
> and hard to tell if the command did anything without using other
> commands like `git log <commit>` to check if the reword was done.
> 
> Print a message on successful rewords so the user has feedback about it.

I dunno about this one. My take here is that a command should be silent
unless it has something to say, for example when it couldn't honor the
user's request [1].

> diff --git a/builtin/history.c b/builtin/history.c
> index 51a22a9a1c..0f1ba3b531 100644
> --- a/builtin/history.c
> +++ b/builtin/history.c
> @@ -739,6 +739,10 @@ static int cmd_history_reword(int argc,
>  		goto out;
>  	}
>  
> +	fprintf(stderr, _("Successfully reworded commit %s to %s\n"),
> +		repo_find_unique_abbrev(repo, &original->object.oid, DEFAULT_ABBREV),
> +		repo_find_unique_abbrev(repo, &rewritten->object.oid, DEFAULT_ABBREV));
> +

Seeing the implementation also raises a couple of questions:

  - Why do we mention the rewritten commit, only? Shouldn't we also
    print the changed HEAD?

  - Why don't we print any of the other rewritten branches?

  - What makes "git history reword" so special as compared to for
    example "git history fixup" or "git history split" so that it needs
    a message while the others don't?

It might make sense to maybe introduce a verbose mode where we do print
such information. But if so, we should have good answers to the above
questions and implement this in a way that makes sense for the other
subcommands, too, so that we can apply the same principle to all of
them.

Thanks!

Patrick

[1]: https://www.linfo.org/rule_of_silence.html

^ permalink raw reply

* [PATCH GSoC RFC v12 00/12] cat-file: add remote-object-info to batch-command
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20250221190451.12536-1-eric.peijian@gmail.com>

This path series is a continuation of Eric Ju's (eric.peijian@gmail.com) and
Calvin Wan's (calvinwan@google.com) patch series [1] and [2] respectively.

Sometimes it is beneficial to retrieve information about an object without
having to download it completely. The server logic for retrieving size has
already been implemented and merged in "a2ba162cda (object-info: support for
retrieving object info, 2021-04-20)"[3]. This patch series implement the client
option for it.

Eric's series adds the `remote-object-info` command to
`cat-file --batch-command`. This command allows the client to make an
object-info command request to a server that supports protocol v2.

If the server uses protocol v2 but does not support the object-info capability,
`cat-file --batch-command` will die.

If a user attempts to use `remote-object-info` with protocol v1,
`cat-file --batch-command` will die.

Currently, only the size (%(objectsize)) is supported end to end in this
implementation. The type (%(objecttype)) is known by the client's allow-list
and request path but is not supported on the server side nor the response
parsing. A follow up series will add full end-to-end support for %(objecttype).

The default format for remote-object-info is set to %(objectname) %(objectsize).
Once %(objecttype) is supported, the default format will be unified accordingly.

If the batch command format includes unsupported fields such as %(objecttype),
%(objectsize:disk), or %(deltabase), the command will return empty strings for
each unsupported field.

This series completes Eric's work mainly with the refactor of the validation
of the placeholder with an allow-list that filters what the client asks with
what the server is capable of provide following Jeff King's idea [4].

I have a question for the design:

1. If the format includes unsupported fields such as %(objecttype) or
   %(deltabase) it currently returns an empty string for each unsupported
   field, this follows what for-each-ref does with known but inapplicable
   atoms. However future placeholders that will be implemented: %(rest),
   %(objectmode) can return empty strings. How should we differentiate
   "unsupported" vs "no data".
   Eric proposed to use a placeholder like "???" [5].

[1]: https://lore.kernel.org/git/20250221190451.12536-1-eric.peijian@gmail.com/
[2]: https://lore.kernel.org/git/20220728230210.2952731-1-calvinwan@google.com/#t
[3]: https://git.kernel.org/pub/scm/git/git.git/commit/?id=a2ba162cda2acc171c3e36acbbc854792b093cb7
[4]: https://lore.kernel.org/git/20250313060250.GH94015@coredump.intra.peff.net/
[5]: https://lore.kernel.org/git/CAN2LT1D3d=yMYVhBjpj5PvyjfTVjwqcFPNViuCJ=f49YbCZuJg@mail.gmail.com/

Changes since v11:

- Rebased onto current master.
- Added fetch-object-info.c to meson.build.
- Added t1017-cat-file-remote-object-info.sh to t/meson.build.
- Fixed style feedback from v10.
- Replaced strstr() validation with a dynamic allow-list in
  expand_atom() based on server-advertised capabilities, filtering
  unsupported options in fetch_object_info() before sending.
- Unsupported placeholders return empty strings instead of die().
- Initialize data->type to OBJ_BAD with NULL check on type_name().
- Moved global variables to local scope in parse_cmd_remote_object_info.
- Decoupled batch_object_write() from sizep so output is always produced.
- Added remote_atom_map[] for protocol-to-atom name mapping.
- Included "type" in the client request path for forward-compatibility.
- Fixed memory leak of data->name in transport-helper disconnect.
- Changed error message "not our ref" to "server does not recognize object".
- Split fetch-pack refactoring into two commits (move + refactor).
- Updated caveats documentation and tests.

Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
Calvin Wan (3):
      fetch-pack: move fetch initialization
      serve: advertise object-info feature
      transport: add client support for object-info

Eric Ju (4):
      git-compat-util: add strtoul_ul() with error handling
      cat-file: add declaration of variable i inside its for loop
      t1006: split test utility functions into new "lib-cat-file.sh"
      cat-file: add remote-object-info to batch-command

Pablo Sabater (5):
      transport-helper: fix memory leak of helper on disconnect
      fetch-pack: move function to connect.c
      connect: refactor packet writing
      cat-file: validate remote atoms with allow_list
      cat-file: make remote-object-info allow-list dynamic

 Documentation/git-cat-file.adoc        |  25 +-
 Makefile                               |   1 +
 builtin/cat-file.c                     | 191 ++++++++-
 connect.c                              |  34 ++
 connect.h                              |   8 +
 fetch-object-info.c                    |  93 +++++
 fetch-object-info.h                    |  22 ++
 fetch-pack.c                           |  51 +--
 fetch-pack.h                           |   2 +
 git-compat-util.h                      |  20 +
 meson.build                            |   1 +
 object-file.c                          |  10 +
 odb.h                                  |   3 +
 serve.c                                |   5 +-
 t/lib-cat-file.sh                      |  16 +
 t/meson.build                          |   1 +
 t/t1006-cat-file.sh                    |  13 +-
 t/t1017-cat-file-remote-object-info.sh | 684 +++++++++++++++++++++++++++++++++
 transport-helper.c                     |  13 +-
 transport.c                            |  28 +-
 transport.h                            |  11 +
 21 files changed, 1158 insertions(+), 74 deletions(-)
---
base-commit: 9ac3f193c05c2237e2b14ebaa1149e9fc8a1abe0
change-id: 20260608-ps-eric-work-rebase-b73ae84ba671

Best regards,
--  
Pablo Sabater <pabloosabaterr@gmail.com>

^ permalink raw reply

* [PATCH GSoC RFC v12 01/12] transport-helper: fix memory leak of helper on disconnect
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20260608-ps-eric-work-rebase-v12-0-5338b766e658@gmail.com>

disconnect_helper() only frees data inside of the if(data->helper)
block [1]. When the transport is disconnected without the helper
being fully started, data->name allocated in transport_helper_init()
is never freed.

Move FREE_AND_NULL(data->name) outside the conditional block so it's
always freed on disconnect.

[1]: https://lore.kernel.org/git/05fbadbae2184479c87c37675dde7bd79b3e32ab.1716465556.git.ps@pks.im/

Mentored-by: Karthik Nayak <karthik.188@gmail.com>
Mentored-by: Chandra Pratap <chandrapratap3519@gmail.com>
Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 transport-helper.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/transport-helper.c b/transport-helper.c
index 04d55572a9..20a6ea8f81 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -266,9 +266,9 @@ static int disconnect_helper(struct transport *transport)
 		close(data->helper->out);
 		fclose(data->out);
 		res = finish_command(data->helper);
-		FREE_AND_NULL(data->name);
 		FREE_AND_NULL(data->helper);
 	}
+	FREE_AND_NULL(data->name);
 	return res;
 }
 

-- 
2.54.0

^ permalink raw reply related

* [PATCH GSoC RFC v12 02/12] git-compat-util: add strtoul_ul() with error handling
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20260608-ps-eric-work-rebase-v12-0-5338b766e658@gmail.com>

From: Eric Ju <eric.peijian@gmail.com>

We already have strtoul_ui() and similar functions that provide proper
error handling using strtoul from the standard library. However,
there isn't currently a variant that returns an unsigned long.

This variant is needed in a subsequent commit.

Add  strtoul_ul() to address this gap, enabling the
return of an unsigned long with proper error handling.

Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 git-compat-util.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/git-compat-util.h b/git-compat-util.h
index 8809776407..4bf569f35c 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -975,6 +975,26 @@ static inline int strtoul_ui(char const *s, int base, unsigned int *result)
 	return 0;
 }
 
+/*
+ * Convert a string to an unsigned long using the standard library's strtoul,
+ * with additional error handling to ensure robustness.
+ */
+static inline int strtoul_ul(char const *s, int base, unsigned long *result)
+{
+	unsigned long ul;
+	char *p;
+
+	errno = 0;
+	/* negative values would be accepted by strtoul */
+	if (strchr(s, '-'))
+		return -1;
+	ul = strtoul(s, &p, base);
+	if (errno || *p || p == s)
+		return -1;
+	*result = ul;
+	return 0;
+}
+
 static inline int strtol_i(char const *s, int base, int *result)
 {
 	long ul;

-- 
2.54.0

^ permalink raw reply related

* [PATCH GSoC RFC v12 03/12] cat-file: add declaration of variable i inside its for loop
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20260608-ps-eric-work-rebase-v12-0-5338b766e658@gmail.com>

From: Eric Ju <eric.peijian@gmail.com>

Some code used in this series declares variable i and only uses it
in a for loop, not in any other logic outside the loop.

Change the declaration of i to be inside the for loop for readability.
While at it, we also change its type from "int" to "size_t" where the latter makes more sense.

Helped-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Eric Ju <eric.peijian@gmail.com>
Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 builtin/cat-file.c | 11 +++--------
 fetch-pack.c       |  3 +--
 2 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index fa45f774d7..c060fd4800 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -726,12 +726,10 @@ static void dispatch_calls(struct batch_options *opt,
 		struct queued_cmd *cmd,
 		int nr)
 {
-	int i;
-
 	if (!opt->buffer_output)
 		die(_("flush is only for --buffer mode"));
 
-	for (i = 0; i < nr; i++)
+	for (size_t i = 0; i < nr; i++)
 		cmd[i].fn(opt, cmd[i].line, output, data);
 
 	fflush(stdout);
@@ -739,9 +737,7 @@ static void dispatch_calls(struct batch_options *opt,
 
 static void free_cmds(struct queued_cmd *cmd, size_t *nr)
 {
-	size_t i;
-
-	for (i = 0; i < *nr; i++)
+	for (size_t i = 0; i < *nr; i++)
 		FREE_AND_NULL(cmd[i].line);
 
 	*nr = 0;
@@ -768,7 +764,6 @@ static void batch_objects_command(struct batch_options *opt,
 	size_t alloc = 0, nr = 0;
 
 	while (strbuf_getdelim_strip_crlf(&input, stdin, opt->input_delim) != EOF) {
-		int i;
 		const struct parse_cmd *cmd = NULL;
 		const char *p = NULL, *cmd_end;
 		struct queued_cmd call = {0};
@@ -778,7 +773,7 @@ static void batch_objects_command(struct batch_options *opt,
 		if (isspace(*input.buf))
 			die(_("whitespace before command: '%s'"), input.buf);
 
-		for (i = 0; i < ARRAY_SIZE(commands); i++) {
+		for (size_t i = 0; i < ARRAY_SIZE(commands); i++) {
 			if (!skip_prefix(input.buf, commands[i].name, &cmd_end))
 				continue;
 
diff --git a/fetch-pack.c b/fetch-pack.c
index 120e01f3cf..f13951d154 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1388,9 +1388,8 @@ static void write_fetch_command_and_capabilities(struct strbuf *req_buf,
 	if (advertise_sid && server_supports_v2("session-id"))
 		packet_buf_write(req_buf, "session-id=%s", trace2_session_id());
 	if (server_options && server_options->nr) {
-		int i;
 		ensure_server_supports_v2("server-option");
-		for (i = 0; i < server_options->nr; i++)
+		for (size_t i = 0; i < server_options->nr; i++)
 			packet_buf_write(req_buf, "server-option=%s",
 					 server_options->items[i].string);
 	}

-- 
2.54.0

^ permalink raw reply related

* [PATCH GSoC RFC v12 04/12] t1006: split test utility functions into new "lib-cat-file.sh"
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20260608-ps-eric-work-rebase-v12-0-5338b766e658@gmail.com>

From: Eric Ju <eric.peijian@gmail.com>

This refactor extracts utility functions from the cat-file's test
script "t1006-cat-file.sh" into a new "lib-cat-file.sh" dedicated
library file. The goal is to improve code reuse and readability,
enabling future tests to leverage these utilities without duplicating
code.

Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 t/lib-cat-file.sh   | 16 ++++++++++++++++
 t/t1006-cat-file.sh | 13 +------------
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/t/lib-cat-file.sh b/t/lib-cat-file.sh
new file mode 100644
index 0000000000..44af232d74
--- /dev/null
+++ b/t/lib-cat-file.sh
@@ -0,0 +1,16 @@
+# Library of git-cat-file related test functions.
+
+# Print a string without a trailing newline.
+echo_without_newline () {
+	printf '%s' "$*"
+}
+
+# Print a string without newlines and replace them with a NULL character (\0).
+echo_without_newline_nul () {
+	echo_without_newline "$@" | tr '\n' '\0'
+}
+
+# Calculate the length of a string.
+strlen () {
+	echo_without_newline "$1" | wc -c | sed -e 's/^ *//'
+}
diff --git a/t/t1006-cat-file.sh b/t/t1006-cat-file.sh
index 8e2c52652c..8360f3bbd9 100755
--- a/t/t1006-cat-file.sh
+++ b/t/t1006-cat-file.sh
@@ -4,6 +4,7 @@ test_description='git cat-file'
 
 . ./test-lib.sh
 . "$TEST_DIRECTORY/lib-loose.sh"
+. "$TEST_DIRECTORY"/lib-cat-file.sh
 
 test_cmdmode_usage () {
 	test_expect_code 129 "$@" 2>err &&
@@ -99,18 +100,6 @@ do
 	'
 done
 
-echo_without_newline () {
-    printf '%s' "$*"
-}
-
-echo_without_newline_nul () {
-	echo_without_newline "$@" | tr '\n' '\0'
-}
-
-strlen () {
-    echo_without_newline "$1" | wc -c | sed -e 's/^ *//'
-}
-
 run_tests () {
     type=$1
     object_name="$2"

-- 
2.54.0

^ permalink raw reply related

* [PATCH GSoC RFC v12 05/12] fetch-pack: move function to connect.c
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20260608-ps-eric-work-rebase-v12-0-5338b766e658@gmail.com>

write_fetch_command_and_capabilities will be refactored in a subsequent
commit where it will become a more general-purpose function, making it
more accessible to additional commands in the future.

To move `write_fetch_command_and_capabilities()` to `connect.c`, we need
to adjust how `advertise_sid` is managed. Previously in `fetch_pack.c`,
`advertise_sid` was a static variable, modified using
`repo_config_get_bool()`.

In `connect.c`, we now initialize `advertise_sid` at the begining by
directly using `repo_config_get_bool()`. This change is safe because:

In the original `fetch-pack.c` code, there are only two places that write
`advertise_sid`:

1. In function `do_fetch_pack()`:
        if (!sever_supports("session_id"))
               advertise_sid = 0;
2. In function `fetch_pack_config()`:
        repo_config_get_bool("transfer.advertisesid", &advertise_sid);

About 1, since `do_fetch_pack()` is only relevant for protocol v1, this
assignment can be ignored, as `write_fetch_command_and_capabilities()`
is only used in v2.

About 2, `repo_config_get_bool()` is from `config.h` and it's an out-of-box
dependency of `connect.c`, so we can reuse it directly.

Move `write_fetch_command_and_capabilities()` to `connect.c`

Helped-by: Jonathan Tan <jonathantanmy@google.com>
Helped-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Eric Ju <eric.peijian@gmail.com>
Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 connect.c    | 34 ++++++++++++++++++++++++++++++++++
 connect.h    |  4 ++++
 fetch-pack.c | 31 -------------------------------
 3 files changed, 38 insertions(+), 31 deletions(-)

diff --git a/connect.c b/connect.c
index 47e39d2a73..1dced8e632 100644
--- a/connect.c
+++ b/connect.c
@@ -700,6 +700,40 @@ int server_supports(const char *feature)
 	return !!server_feature_value(feature, NULL);
 }
 
+void write_fetch_command_and_capabilities(struct strbuf *req_buf,
+					  const struct string_list *server_options)
+{
+	const char *hash_name;
+	int advertise_sid;
+
+	repo_config_get_bool(the_repository, "transfer.advertisesid", &advertise_sid);
+
+	ensure_server_supports_v2("fetch");
+	packet_buf_write(req_buf, "command=fetch");
+	if (server_supports_v2("agent"))
+		packet_buf_write(req_buf, "agent=%s", git_user_agent_sanitized());
+	if (advertise_sid && server_supports_v2("session-id"))
+		packet_buf_write(req_buf, "session-id=%s", trace2_session_id());
+	if (server_options && server_options->nr) {
+		ensure_server_supports_v2("server-option");
+		for (size_t i = 0; i < server_options->nr; i++)
+			packet_buf_write(req_buf, "server-option=%s",
+					 server_options->items[i].string);
+	}
+
+	if (server_feature_v2("object-format", &hash_name)) {
+		const unsigned int hash_algo = hash_algo_by_name(hash_name);
+		if (hash_algo_by_ptr(the_hash_algo) != hash_algo)
+			die(_("mismatched algorithms: client %s; server %s"),
+			    the_hash_algo->name, hash_name);
+		packet_buf_write(req_buf, "object-format=%s", the_hash_algo->name);
+	} else if (hash_algo_by_ptr(the_hash_algo) != GIT_HASH_SHA1_LEGACY) {
+		die(_("the server does not support algorithm '%s'"),
+		    the_hash_algo->name);
+	}
+	packet_buf_delim(req_buf);
+}
+
 static const char *url_scheme_name(enum url_scheme scheme)
 {
 	switch (scheme) {
diff --git a/connect.h b/connect.h
index aa482a37fb..c4f6ea4b0a 100644
--- a/connect.h
+++ b/connect.h
@@ -34,4 +34,8 @@ void check_stateless_delimiter(int stateless_rpc,
 			       struct packet_reader *reader,
 			       const char *error);
 
+struct string_list;
+void write_fetch_command_and_capabilities(struct strbuf *req_buf,
+					  const struct string_list *server_options);
+
 #endif
diff --git a/fetch-pack.c b/fetch-pack.c
index f13951d154..4a8a70b5f3 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1376,37 +1376,6 @@ static int add_haves(struct fetch_negotiator *negotiator,
 	return haves_added;
 }
 
-static void write_fetch_command_and_capabilities(struct strbuf *req_buf,
-						 const struct string_list *server_options)
-{
-	const char *hash_name;
-
-	ensure_server_supports_v2("fetch");
-	packet_buf_write(req_buf, "command=fetch");
-	if (server_supports_v2("agent"))
-		packet_buf_write(req_buf, "agent=%s", git_user_agent_sanitized());
-	if (advertise_sid && server_supports_v2("session-id"))
-		packet_buf_write(req_buf, "session-id=%s", trace2_session_id());
-	if (server_options && server_options->nr) {
-		ensure_server_supports_v2("server-option");
-		for (size_t i = 0; i < server_options->nr; i++)
-			packet_buf_write(req_buf, "server-option=%s",
-					 server_options->items[i].string);
-	}
-
-	if (server_feature_v2("object-format", &hash_name)) {
-		int hash_algo = hash_algo_by_name(hash_name);
-		if (hash_algo_by_ptr(the_hash_algo) != hash_algo)
-			die(_("mismatched algorithms: client %s; server %s"),
-			    the_hash_algo->name, hash_name);
-		packet_buf_write(req_buf, "object-format=%s", the_hash_algo->name);
-	} else if (hash_algo_by_ptr(the_hash_algo) != GIT_HASH_SHA1_LEGACY) {
-		die(_("the server does not support algorithm '%s'"),
-		    the_hash_algo->name);
-	}
-	packet_buf_delim(req_buf);
-}
-
 static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 			      struct fetch_pack_args *args,
 			      const struct ref *wants, struct oidset *common,

-- 
2.54.0

^ permalink raw reply related

* [PATCH GSoC RFC v12 06/12] connect: refactor packet writing
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20260608-ps-eric-work-rebase-v12-0-5338b766e658@gmail.com>

Refactor `write_fetch_command_and_capabilities()`, enabling it to serve
both fetch and additional commands.

In this context, "command" refers to the "operations" supported by
Git's wire protocol https://git-scm.com/docs/protocol-v2, such as a Git
subcommand (e.g., git-fetch(1)) or a server-side operation like
"object-info" as implemented in commit a2ba162
(object-info: support for retrieving object info, 2021-04-20).

Refactor the function signature to accept a command instead of the
hardcoded "fetch".

Helped-by: Jonathan Tan <jonathantanmy@google.com>
Helped-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Eric Ju <eric.peijian@gmail.com>
Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 connect.c    | 10 +++++-----
 connect.h    |  8 ++++++--
 fetch-pack.c |  4 ++--
 3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/connect.c b/connect.c
index 1dced8e632..78c69d4485 100644
--- a/connect.c
+++ b/connect.c
@@ -700,16 +700,16 @@ int server_supports(const char *feature)
 	return !!server_feature_value(feature, NULL);
 }
 
-void write_fetch_command_and_capabilities(struct strbuf *req_buf,
-					  const struct string_list *server_options)
+void write_command_and_capabilities(struct strbuf *req_buf, const char *command,
+				    const struct string_list *server_options)
 {
 	const char *hash_name;
 	int advertise_sid;
 
 	repo_config_get_bool(the_repository, "transfer.advertisesid", &advertise_sid);
 
-	ensure_server_supports_v2("fetch");
-	packet_buf_write(req_buf, "command=fetch");
+	ensure_server_supports_v2(command);
+	packet_buf_write(req_buf, "command=%s", command);
 	if (server_supports_v2("agent"))
 		packet_buf_write(req_buf, "agent=%s", git_user_agent_sanitized());
 	if (advertise_sid && server_supports_v2("session-id"))
@@ -727,7 +727,7 @@ void write_fetch_command_and_capabilities(struct strbuf *req_buf,
 			die(_("mismatched algorithms: client %s; server %s"),
 			    the_hash_algo->name, hash_name);
 		packet_buf_write(req_buf, "object-format=%s", the_hash_algo->name);
-	} else if (hash_algo_by_ptr(the_hash_algo) != GIT_HASH_SHA1_LEGACY) {
+	} else if (hash_algo_by_ptr(the_hash_algo) != GIT_HASH_SHA1) {
 		die(_("the server does not support algorithm '%s'"),
 		    the_hash_algo->name);
 	}
diff --git a/connect.h b/connect.h
index c4f6ea4b0a..8f4c523892 100644
--- a/connect.h
+++ b/connect.h
@@ -34,8 +34,12 @@ void check_stateless_delimiter(int stateless_rpc,
 			       struct packet_reader *reader,
 			       const char *error);
 
+/*
+ * Writes a command along with the requested server capabilities/features into a
+ * request buffer.
+ */
 struct string_list;
-void write_fetch_command_and_capabilities(struct strbuf *req_buf,
-					  const struct string_list *server_options);
+void write_command_and_capabilities(struct strbuf *req_buf, const char *command,
+				    const struct string_list *server_options);
 
 #endif
diff --git a/fetch-pack.c b/fetch-pack.c
index 4a8a70b5f3..3d32114907 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1387,7 +1387,7 @@ static int send_fetch_request(struct fetch_negotiator *negotiator, int fd_out,
 	int done_sent = 0;
 	struct strbuf req_buf = STRBUF_INIT;
 
-	write_fetch_command_and_capabilities(&req_buf, args->server_options);
+	write_command_and_capabilities(&req_buf, "fetch", args->server_options);
 
 	if (args->use_thin_pack)
 		packet_buf_write(&req_buf, "thin-pack");
@@ -2255,7 +2255,7 @@ void negotiate_using_fetch(const struct oid_array *negotiation_restrict_tips,
 					   the_repository, "%d",
 					   negotiation_round);
 		strbuf_reset(&req_buf);
-		write_fetch_command_and_capabilities(&req_buf, server_options);
+		write_command_and_capabilities(&req_buf, "fetch", server_options);
 
 		packet_buf_write(&req_buf, "wait-for-done");
 

-- 
2.54.0

^ permalink raw reply related

* [PATCH GSoC RFC v12 07/12] fetch-pack: move fetch initialization
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20260608-ps-eric-work-rebase-v12-0-5338b766e658@gmail.com>

From: Calvin Wan <calvinwan@google.com>

There are some variables initialized at the start of the
do_fetch_pack_v2() state machine. Currently, they are initialized
in FETCH_CHECK_LOCAL, which is the initial state set at the beginning
of the function.

However, a subsequent patch will allow for another initial state,
while still requiring these initialized variables.
Move the initialization to be before the state machine,
so that they are set regardless of the initial state.

Note that there is no change in behavior, because we're moving code
from the beginning of the first state to just before the execution of
the state machine.

Helped-by: Jonathan Tan <jonathantanmy@google.com>
Helped-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Eric Ju <eric.peijian@gmail.com>
Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 fetch-pack.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/fetch-pack.c b/fetch-pack.c
index 3d32114907..cdebd3476f 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1736,18 +1736,18 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 		reader.me = "fetch-pack";
 	}
 
+	/* v2 supports these by default */
+	allow_unadvertised_object_request |= ALLOW_REACHABLE_SHA1;
+	use_sideband = 2;
+	if (args->depth > 0 || args->deepen_since || args->deepen_not)
+		args->deepen = 1;
+
 	while (state != FETCH_DONE) {
 		switch (state) {
 		case FETCH_CHECK_LOCAL:
 			sort_ref_list(&ref, ref_compare_name);
 			QSORT(sought, nr_sought, cmp_ref_by_name);
 
-			/* v2 supports these by default */
-			allow_unadvertised_object_request |= ALLOW_REACHABLE_SHA1;
-			use_sideband = 2;
-			if (args->depth > 0 || args->deepen_since || args->deepen_not)
-				args->deepen = 1;
-
 			/* Filter 'ref' by 'sought' and those that aren't local */
 			mark_complete_and_common_ref(negotiator, args, &ref);
 			filter_refs(args, &ref, sought, nr_sought);

-- 
2.54.0

^ permalink raw reply related

* [PATCH GSoC RFC v12 08/12] serve: advertise object-info feature
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20260608-ps-eric-work-rebase-v12-0-5338b766e658@gmail.com>

From: Calvin Wan <calvinwan@google.com>

In order for a client to know what object-info components a server can
provide, advertise supported object-info features. This will allow a
client to decide whether to query the server for object-info or fetch
as a fallback.

Helped-by: Jonathan Tan <jonathantanmy@google.com>
Helped-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Eric Ju <eric.peijian@gmail.com>
Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 serve.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/serve.c b/serve.c
index 49a6e39b1d..2b07d922b3 100644
--- a/serve.c
+++ b/serve.c
@@ -89,7 +89,7 @@ static void session_id_receive(struct repository *r UNUSED,
 	trace2_data_string("transfer", NULL, "client-sid", client_sid);
 }
 
-static int object_info_advertise(struct repository *r, struct strbuf *value UNUSED)
+static int object_info_advertise(struct repository *r, struct strbuf *value)
 {
 	if (advertise_object_info == -1 &&
 	    repo_config_get_bool(r, "transfer.advertiseobjectinfo",
@@ -97,6 +97,9 @@ static int object_info_advertise(struct repository *r, struct strbuf *value UNUS
 		/* disabled by default */
 		advertise_object_info = 0;
 	}
+	/* Currently only size is supported */
+	if (value && advertise_object_info)
+		strbuf_addstr(value, "size");
 	return advertise_object_info;
 }
 

-- 
2.54.0

^ permalink raw reply related

* [PATCH GSoC RFC v12 09/12] transport: add client support for object-info
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20260608-ps-eric-work-rebase-v12-0-5338b766e658@gmail.com>

From: Calvin Wan <calvinwan@google.com>

Sometimes, it is beneficial to retrieve information about an object
without downloading it entirely. The server-side logic for this
functionality was implemented in commit "a2ba162cda (object-info:
support for retrieving object info, 2021-04-20)." And the wire
format is documented at
https://git-scm.com/docs/protocol-v2#_object_info.

This commit introduces client functions to interact with the server.

Currently, the client supports requesting a list of object IDs with
the 'size' feature from a v2 server. If the server does not advertise
this feature (i.e., transfer.advertiseobjectinfo is set to false),
the client will return an error and exit.

Notice that the entire request is written into req_buf before being
sent to the remote. This approach follows the pattern used in the
`send_fetch_request()` logic within fetch-pack.c.
Streaming the request is not addressed in this patch.

Helped-by: Jonathan Tan <jonathantanmy@google.com>
Helped-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Eric Ju <eric.peijian@gmail.com>
Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 Makefile            |  1 +
 fetch-object-info.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 fetch-object-info.h | 22 ++++++++++++++
 fetch-pack.c        |  3 ++
 fetch-pack.h        |  2 ++
 meson.build         |  1 +
 transport-helper.c  | 11 +++++--
 transport.c         | 28 ++++++++++++++++-
 transport.h         | 11 +++++++
 9 files changed, 163 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index b31ecb0756..45453e03c5 100644
--- a/Makefile
+++ b/Makefile
@@ -1159,6 +1159,7 @@ LIB_OBJS += ewah/ewah_rlw.o
 LIB_OBJS += exec-cmd.o
 LIB_OBJS += fetch-negotiator.o
 LIB_OBJS += fetch-pack.o
+LIB_OBJS += fetch-object-info.o
 LIB_OBJS += fmt-merge-msg.o
 LIB_OBJS += fsck.o
 LIB_OBJS += fsmonitor.o
diff --git a/fetch-object-info.c b/fetch-object-info.c
new file mode 100644
index 0000000000..51a898430d
--- /dev/null
+++ b/fetch-object-info.c
@@ -0,0 +1,87 @@
+#include "git-compat-util.h"
+#include "gettext.h"
+#include "hex.h"
+#include "pkt-line.h"
+#include "connect.h"
+#include "oid-array.h"
+#include "odb.h"
+#include "fetch-object-info.h"
+#include "string-list.h"
+
+/* Sends git-cat-file object-info command and its arguments into the request buffer. */
+static void send_object_info_request(const int fd_out, struct object_info_args *args)
+{
+	struct strbuf req_buf = STRBUF_INIT;
+
+	write_command_and_capabilities(&req_buf, "object-info", args->server_options);
+
+	if (unsorted_string_list_has_string(args->object_info_options, "size"))
+		packet_buf_write(&req_buf, "size");
+
+	if (args->oids)
+		for (size_t i = 0; i < args->oids->nr; i++)
+			packet_buf_write(&req_buf, "oid %s", oid_to_hex(&args->oids->oid[i]));
+
+	packet_buf_flush(&req_buf);
+	if (write_in_full(fd_out, req_buf.buf, req_buf.len) < 0)
+		die_errno(_("unable to write request to remote"));
+
+	strbuf_release(&req_buf);
+}
+
+int fetch_object_info(const enum protocol_version version, struct object_info_args *args,
+		      struct packet_reader *reader, struct object_info *object_info_data,
+		      const int stateless_rpc, const int fd_out)
+{
+	int size_index = -1;
+
+	switch (version) {
+	case protocol_v2:
+		if (!server_supports_v2("object-info"))
+			die(_("object-info capability is not enabled on the server"));
+		send_object_info_request(fd_out, args);
+		break;
+	case protocol_v1:
+	case protocol_v0:
+		die(_("unsupported protocol version. expected v2"));
+	case protocol_unknown_version:
+		BUG("unknown protocol version");
+	}
+
+	for (size_t i = 0; i < args->object_info_options->nr; i++) {
+		if (packet_reader_read(reader) != PACKET_READ_NORMAL) {
+			check_stateless_delimiter(stateless_rpc, reader, "stateless delimiter expected");
+			return -1;
+		}
+
+		if (!string_list_has_string(args->object_info_options, reader->line))
+			return -1;
+
+		if (!strcmp(reader->line, "size")) {
+			size_index = i;
+			for (size_t j = 0; j < args->oids->nr; j++)
+				object_info_data[j].sizep = xcalloc(1, sizeof(*object_info_data[j].sizep));
+		}
+	}
+
+	for (size_t i = 0; packet_reader_read(reader) == PACKET_READ_NORMAL && i < args->oids->nr; i++) {
+		struct string_list object_info_values = STRING_LIST_INIT_DUP;
+
+		string_list_split(&object_info_values, reader->line, " ", -1);
+		if (0 <= size_index) {
+			if (!strcmp(object_info_values.items[1 + size_index].string, ""))
+				die("object-info: server does not recognize object %s",
+				    object_info_values.items[0].string);
+
+			if (strtoul_ul(object_info_values.items[1 + size_index].string, 10, object_info_data[i].sizep))
+				die("object-info: ref %s has invalid size %s",
+				    object_info_values.items[0].string,
+				    object_info_values.items[1 + size_index].string);
+		}
+
+		string_list_clear(&object_info_values, 0);
+	}
+	check_stateless_delimiter(stateless_rpc, reader, "stateless delimiter expected");
+
+	return 0;
+}
diff --git a/fetch-object-info.h b/fetch-object-info.h
new file mode 100644
index 0000000000..d35284bd6b
--- /dev/null
+++ b/fetch-object-info.h
@@ -0,0 +1,22 @@
+#ifndef FETCH_OBJECT_INFO_H
+#define FETCH_OBJECT_INFO_H
+
+#include "pkt-line.h"
+#include "protocol.h"
+#include "odb.h"
+
+struct object_info_args {
+	struct string_list *object_info_options;
+	const struct string_list *server_options;
+	struct oid_array *oids;
+};
+
+/*
+ * Sends git-cat-file object-info command into the request buf and read the
+ * results from packets.
+ */
+int fetch_object_info(enum protocol_version version, struct object_info_args *args,
+		      struct packet_reader *reader, struct object_info *object_info_data,
+		      int stateless_rpc, int fd_out);
+
+#endif /* FETCH_OBJECT_INFO_H */
diff --git a/fetch-pack.c b/fetch-pack.c
index cdebd3476f..a86c93fc52 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -1742,6 +1742,9 @@ static struct ref *do_fetch_pack_v2(struct fetch_pack_args *args,
 	if (args->depth > 0 || args->deepen_since || args->deepen_not)
 		args->deepen = 1;
 
+	if (args->object_info)
+		state = FETCH_SEND_REQUEST;
+
 	while (state != FETCH_DONE) {
 		switch (state) {
 		case FETCH_CHECK_LOCAL:
diff --git a/fetch-pack.h b/fetch-pack.h
index 6d0dec7f41..5a428f11ed 100644
--- a/fetch-pack.h
+++ b/fetch-pack.h
@@ -16,6 +16,7 @@ struct fetch_pack_args {
 	const struct string_list *deepen_not;
 	struct list_objects_filter_options filter_options;
 	const struct string_list *server_options;
+	struct object_info *object_info_data;
 
 	/*
 	 * If not NULL, during packfile negotiation, fetch-pack will send "have"
@@ -43,6 +44,7 @@ struct fetch_pack_args {
 	unsigned reject_shallow_remote:1;
 	unsigned deepen:1;
 	unsigned refetch:1;
+	unsigned object_info:1;
 
 	/*
 	 * Indicate that the remote of this request is a promisor remote. The
diff --git a/meson.build b/meson.build
index 064fe2e2f1..7b7dec5949 100644
--- a/meson.build
+++ b/meson.build
@@ -347,6 +347,7 @@ libgit_sources = [
   'exec-cmd.c',
   'fetch-negotiator.c',
   'fetch-pack.c',
+  'fetch-object-info.c',
   'fmt-merge-msg.c',
   'fsck.c',
   'fsmonitor.c',
diff --git a/transport-helper.c b/transport-helper.c
index 20a6ea8f81..4adb73bfbc 100644
--- a/transport-helper.c
+++ b/transport-helper.c
@@ -727,8 +727,8 @@ static int fetch_refs(struct transport *transport,
 
 	/*
 	 * If we reach here, then the server, the client, and/or the transport
-	 * helper does not support protocol v2. --negotiate-only requires
-	 * protocol v2.
+	 * helper does not support protocol v2. --negotiate-only and cat-file
+	 * remote-object-info require protocol v2.
 	 */
 	if (data->transport_options.acked_commits) {
 		warning(_("--negotiate-only requires protocol v2"));
@@ -744,6 +744,13 @@ static int fetch_refs(struct transport *transport,
 		free_refs(dummy);
 	}
 
+	/* fail the command explicitly to avoid further commands input. */
+	if (transport->smart_options->object_info)
+		die(_("remote-object-info requires protocol v2"));
+
+	if (!data->get_refs_list_called)
+		get_refs_list_using_list(transport, 0);
+
 	count = 0;
 	for (i = 0; i < nr_heads; i++)
 		if (!(to_fetch[i]->status & REF_STATUS_UPTODATE))
diff --git a/transport.c b/transport.c
index 0f5ec30247..7d3246e12b 100644
--- a/transport.c
+++ b/transport.c
@@ -9,6 +9,7 @@
 #include "hook.h"
 #include "pkt-line.h"
 #include "fetch-pack.h"
+#include "fetch-object-info.h"
 #include "remote.h"
 #include "connect.h"
 #include "send-pack.h"
@@ -467,8 +468,33 @@ static int fetch_refs_via_pack(struct transport *transport,
 	args.negotiation_restrict_tips = data->options.negotiation_restrict_tips;
 	args.negotiation_include_tips = data->options.negotiation_include_tips;
 	args.reject_shallow_remote = transport->smart_options->reject_shallow;
+	args.object_info = transport->smart_options->object_info;
+
+	if (transport->smart_options->object_info
+	    && transport->smart_options->object_info_oids->nr > 0) {
+		struct packet_reader reader;
+		struct object_info_args obj_info_args = { 0 };
+
+		obj_info_args.server_options = transport->server_options;
+		obj_info_args.oids = transport->smart_options->object_info_oids;
+		obj_info_args.object_info_options = transport->smart_options->object_info_options;
+		string_list_sort(obj_info_args.object_info_options);
+
+		connect_setup(transport, 0);
+		packet_reader_init(&reader, data->fd[0], NULL, 0,
+				PACKET_READ_CHOMP_NEWLINE |
+				PACKET_READ_GENTLE_ON_EOF |
+				PACKET_READ_DIE_ON_ERR_PACKET);
+
+		data->version = discover_version(&reader);
+		transport->hash_algo = reader.hash_algo;
+
+		ret = fetch_object_info(data->version, &obj_info_args, &reader,
+					data->options.object_info_data, transport->stateless_rpc,
+					data->fd[1]);
+		goto cleanup;
 
-	if (!data->finished_handshake) {
+	} else if (!data->finished_handshake) {
 		int i;
 		int must_list_refs = 0;
 		for (i = 0; i < nr_heads; i++) {
diff --git a/transport.h b/transport.h
index 7e5867cffa..bd60b10af4 100644
--- a/transport.h
+++ b/transport.h
@@ -6,6 +6,7 @@
 #include "list-objects-filter-options.h"
 #include "string-list.h"
 #include "connect.h"
+#include "odb.h"
 
 struct git_transport_options {
 	unsigned thin : 1;
@@ -31,6 +32,12 @@ struct git_transport_options {
 	 */
 	unsigned connectivity_checked:1;
 
+	/*
+	 * Transport will attempt to retrieve only object-info.
+	 * If object-info is not supported, the operation will error and exit.
+	 */
+	unsigned object_info : 1;
+
 	int depth;
 	const char *deepen_since;
 	const struct string_list *deepen_not;
@@ -55,6 +62,10 @@ struct git_transport_options {
 	 * common commits to this oidset instead of fetching any packfiles.
 	 */
 	struct oidset *acked_commits;
+
+	struct oid_array *object_info_oids;
+	struct object_info *object_info_data;
+	struct string_list *object_info_options;
 };
 
 enum transport_family {

-- 
2.54.0

^ permalink raw reply related

* [PATCH GSoC RFC v12 10/12] cat-file: add remote-object-info to batch-command
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20260608-ps-eric-work-rebase-v12-0-5338b766e658@gmail.com>

From: Eric Ju <eric.peijian@gmail.com>

Since the `info` command in `cat-file --batch-command` prints object
info for a given object, it is natural to add another command in
`cat-file --batch-command` to print object info for a given object
from a remote.

Add `remote-object-info` to `cat-file --batch-command`.

While `info` takes object ids one at a time, this creates
overhead when making requests to a server. So `remote-object-info`
instead can take multiple object ids at once.

The `cat-file --batch-command` command is generally implemented in
the following manner:

 - Receive and parse input from user
 - Call respective function attached to command
 - Get object info, print object info

In --buffer mode, this changes to:

 - Receive and parse input from user
 - Store respective function attached to command in a queue
 - After flush, loop through commands in queue
    - Call respective function attached to command
    - Get object info, print object info

Notice how the getting and printing of object info is accomplished one
at a time. As described above, this creates a problem for making
requests to a server. Therefore, `remote-object-info` is implemented in
the following manner:

 - Receive and parse input from user
 If command is `remote-object-info`:
    - Get object info from remote
    - Loop through and print each object info
 Else:
    - Call respective function attached to command
    - Parse input, get object info, print object info

And finally for --buffer mode `remote-object-info`:
 - Receive and parse input from user
 - Store respective function attached to command in a queue
 - After flush, loop through commands in queue:
    If command is `remote-object-info`:
        - Get object info from remote
        - Loop through and print each object info
    Else:
        - Call respective function attached to command
        - Get object info, print object info

To summarize, `remote-object-info` gets object info from the remote and
then loops through the object info passed in, printing the info.

In order for `remote-object-info` to avoid remote communication
overhead in the non-buffer mode, the objects are passed in as such:

remote-object-info <remote> <oid> <oid> ... <oid>

rather than

remote-object-info <remote> <oid>
remote-object-info <remote> <oid>
...
remote-object-info <remote> <oid>

Helped-by: Jonathan Tan <jonathantanmy@google.com>
Helped-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Calvin Wan <calvinwan@google.com>
Signed-off-by: Eric Ju <eric.peijian@gmail.com>
Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 Documentation/git-cat-file.adoc        |  24 +-
 builtin/cat-file.c                     | 128 ++++++-
 object-file.c                          |  10 +
 odb.h                                  |   3 +
 t/meson.build                          |   1 +
 t/t1017-cat-file-remote-object-info.sh | 664 +++++++++++++++++++++++++++++++++
 transport.c                            |   4 +-
 7 files changed, 827 insertions(+), 7 deletions(-)

diff --git a/Documentation/git-cat-file.adoc b/Documentation/git-cat-file.adoc
index 86b9181599..aba20eb770 100644
--- a/Documentation/git-cat-file.adoc
+++ b/Documentation/git-cat-file.adoc
@@ -169,6 +169,13 @@ info <object>::
 	Print object info for object reference `<object>`. This corresponds to the
 	output of `--batch-check`.
 
+remote-object-info <remote> <object>...::
+	Print object info for object references `<object>` at specified
+	`<remote>` without downloading objects from the remote.
+	Raise an error when the `object-info` capability is not supported by the remote.
+	Raise an error when no object references are provided.
+	This command may be combined with `--buffer`.
+
 flush::
 	Used with `--buffer` to execute all preceding commands that were issued
 	since the beginning or since the last flush was issued. When `--buffer`
@@ -312,7 +319,8 @@ newline. The available atoms are:
 	The full hex representation of the object name.
 
 `objecttype`::
-	The type of the object (the same as `cat-file -t` reports).
+	The type of the object (the same as `cat-file -t` reports). See
+	`CAVEATS` below. Not supported by `remote-object-info`.
 
 `objectmode`::
 	If the specified object has mode information (such as a tree or
@@ -325,13 +333,14 @@ newline. The available atoms are:
 
 `objectsize:disk`::
 	The size, in bytes, that the object takes up on disk. See the
-	note about on-disk sizes in the `CAVEATS` section below.
+	note about on-disk sizes in the `CAVEATS` section below. Not
+	supported by `remote-object-info`.
 
 `deltabase`::
 	If the object is stored as a delta on-disk, this expands to the
 	full hex representation of the delta base object name.
 	Otherwise, expands to the null OID (all zeroes). See `CAVEATS`
-	below.
+	below. Not supported by `remote-object-info`.
 
 `rest`::
 	If this atom is used in the output string, input lines are split
@@ -341,7 +350,10 @@ newline. The available atoms are:
 	line) are output in place of the `%(rest)` atom.
 
 If no format is specified, the default format is `%(objectname)
-%(objecttype) %(objectsize)`.
+%(objecttype) %(objectsize)`, except for `remote-object-info` commands which use
+`%(objectname) %(objectsize)` for now because "%(objecttype)" is not supported yet.
+WARNING: When "%(objecttype)" is supported, the default format WILL be unified, so
+DO NOT RELY on the current default format to stay the same!!!
 
 If `--batch` is specified, or if `--batch-command` is used with the `contents`
 command, the object information is followed by the object contents (consisting
@@ -438,6 +450,10 @@ scripting purposes.
 CAVEATS
 -------
 
+Note that since %(objecttype), %(objectsize:disk) and %(deltabase) are
+currently not supported by the `remote-object-info` command, we will raise
+an error and exit when they appear in the format string.
+
 Note that the sizes of objects on disk are reported accurately, but care
 should be taken in drawing conclusions about which refs or objects are
 responsible for disk usage. The size of a packed non-delta object may be
diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index c060fd4800..a14cfea815 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -29,6 +29,22 @@
 #include "promisor-remote.h"
 #include "mailmap.h"
 #include "write-or-die.h"
+#include "alias.h"
+#include "remote.h"
+#include "transport.h"
+
+/*
+ * Maximum length for a remote URL. While no universal standard exists,
+ * 8K is assumed to be a reasonable limit.
+ */
+#define MAX_REMOTE_URL_LEN (8 * 1024)
+
+/* Maximum number of objects allowed in a single remote-object-info request. */
+#define MAX_ALLOWED_OBJ_LIMIT 10000
+
+/* Maximum input size permitted for the remote-object-info command. */
+#define MAX_REMOTE_OBJ_INFO_LINE \
+	(MAX_REMOTE_URL_LEN + MAX_ALLOWED_OBJ_LIMIT * (GIT_MAX_HEXSZ + 1))
 
 enum batch_mode {
 	BATCH_MODE_CONTENTS,
@@ -639,6 +655,67 @@ static void batch_one_object(const char *obj_name,
 	object_context_release(&ctx);
 }
 
+static int get_remote_info(struct batch_options *opt,
+			   int argc,
+			   const char **argv,
+			   struct object_info **remote_object_info,
+			   struct oid_array *object_info_oids)
+{
+	int retval = 0;
+	struct remote *remote = NULL;
+	struct object_id oid;
+	struct string_list object_info_options = STRING_LIST_INIT_NODUP;
+	static struct transport *gtransport;
+
+	/*
+	 * Change the format to "%(objectname) %(objectsize)" when
+	 * remote-object-info command is used. Once we start supporting objecttype
+	 * the default format should change to DEFAULT_FORMAT.
+	 */
+	if (!opt->format)
+		opt->format = "%(objectname) %(objectsize)";
+
+	remote = remote_get(argv[0]);
+	if (!remote)
+		die(_("must supply valid remote when using remote-object-info"));
+
+	oid_array_clear(object_info_oids);
+	for (int i = 1; i < argc; i++) {
+		if (get_oid_hex(argv[i], &oid))
+			die(_("Not a valid object name %s"), argv[i]);
+		oid_array_append(object_info_oids, &oid);
+	}
+	if (!object_info_oids->nr)
+		die(_("remote-object-info requires objects"));
+
+	gtransport = transport_get(remote, NULL);
+
+	if (!gtransport->smart_options) {
+		retval = -1;
+		goto cleanup;
+	}
+
+	CALLOC_ARRAY(*remote_object_info, object_info_oids->nr);
+	gtransport->smart_options->object_info = 1;
+	gtransport->smart_options->object_info_oids = object_info_oids;
+
+	/* 'objectsize' is the only option currently supported */
+	if (!strstr(opt->format, "%(objectsize)"))
+		die(_("%s is currently not supported with remote-object-info"), opt->format);
+
+	string_list_append(&object_info_options, "size");
+
+	if (object_info_options.nr > 0) {
+		gtransport->smart_options->object_info_options = &object_info_options;
+		gtransport->smart_options->object_info_data = *remote_object_info;
+		retval = transport_fetch_refs(gtransport, NULL);
+	}
+cleanup:
+	string_list_clear(&object_info_options, 0);
+	transport_disconnect(gtransport);
+	return retval;
+}
+
 struct object_cb_data {
 	struct batch_options *opt;
 	struct expand_data *expand;
@@ -720,6 +797,54 @@ static void parse_cmd_mailmap(struct batch_options *opt UNUSED,
 		load_mailmap();
 }
 
+static void parse_cmd_remote_object_info(struct batch_options *opt,
+					 const char *line, struct strbuf *output,
+					 struct expand_data *data)
+{
+	int count;
+	const char **argv;
+	char *line_to_split;
+	static struct object_info *remote_object_info;
+	static struct oid_array object_info_oids = OID_ARRAY_INIT;
+
+	if (strlen(line) >= MAX_REMOTE_OBJ_INFO_LINE)
+		die(_("remote-object-info command too long"));
+
+	line_to_split = xstrdup(line);
+	count = split_cmdline(line_to_split, &argv);
+	if (count < 0)
+		die(_("split remote-object-info command"));
+	if (count - 1 > MAX_ALLOWED_OBJ_LIMIT)
+		die(_("remote-object-info supports at most %d objects"),
+		    MAX_ALLOWED_OBJ_LIMIT);
+
+	if (get_remote_info(opt, count, argv, &remote_object_info,
+			    &object_info_oids))
+		goto cleanup;
+
+	data->skip_object_info = 1;
+	for (size_t i = 0; i < object_info_oids.nr; i++) {
+		data->oid = object_info_oids.oid[i];
+		if (remote_object_info[i].sizep) {
+			/*
+			 * When reaching here, it means remote-object-info can retrieve
+			 * information from server without downloading them.
+			 */
+			data->size = *remote_object_info[i].sizep;
+			opt->batch_mode = BATCH_MODE_INFO;
+			batch_object_write(argv[i + 1], output, opt, data, NULL, 0);
+		}
+	}
+	data->skip_object_info = 0;
+
+cleanup:
+	for (size_t i = 0; i < object_info_oids.nr; i++)
+		free_object_info_contents(&remote_object_info[i]);
+	free(line_to_split);
+	free(argv);
+	free(remote_object_info);
+}
+
 static void dispatch_calls(struct batch_options *opt,
 		struct strbuf *output,
 		struct expand_data *data,
@@ -751,8 +876,9 @@ static const struct parse_cmd {
 } commands[] = {
 	{ "contents", parse_cmd_contents, 1 },
 	{ "info", parse_cmd_info, 1 },
-	{ "flush", NULL, 0 },
 	{ "mailmap", parse_cmd_mailmap, 1 },
+	{ "remote-object-info", parse_cmd_remote_object_info, 1 },
+	{ "flush", NULL, 0 },
 };
 
 static void batch_objects_command(struct batch_options *opt,
diff --git a/object-file.c b/object-file.c
index 90f995d000..9608607847 100644
--- a/object-file.c
+++ b/object-file.c
@@ -2356,3 +2356,13 @@ int odb_source_loose_read_object_stream(struct odb_read_stream **out,
 	free(st);
 	return -1;
 }
+
+void free_object_info_contents(struct object_info *object_info)
+{
+	if (!object_info)
+		return;
+	free(object_info->typep);
+	free(object_info->sizep);
+	free(object_info->disk_sizep);
+	free(object_info->delta_base_oid);
+}
diff --git a/odb.h b/odb.h
index 73553ed5a7..6d643c5cf3 100644
--- a/odb.h
+++ b/odb.h
@@ -573,4 +573,7 @@ void parse_alternates(const char *string,
 		      const char *relative_base,
 		      struct strvec *out);
 
+/* Free pointers inside of object_info, but not object_info itself */
+void free_object_info_contents(struct object_info *object_info);
+
 #endif /* ODB_H */
diff --git a/t/meson.build b/t/meson.build
index 2af8d01279..3473e477bd 100644
--- a/t/meson.build
+++ b/t/meson.build
@@ -170,6 +170,7 @@ integration_tests = [
   't1014-read-tree-confusing.sh',
   't1015-read-index-unmerged.sh',
   't1016-compatObjectFormat.sh',
+  't1017-cat-file-remote-object-info.sh',
   't1020-subdirectory.sh',
   't1022-read-tree-partial-clone.sh',
   't1050-large.sh',
diff --git a/t/t1017-cat-file-remote-object-info.sh b/t/t1017-cat-file-remote-object-info.sh
new file mode 100755
index 0000000000..5c8c07b0cf
--- /dev/null
+++ b/t/t1017-cat-file-remote-object-info.sh
@@ -0,0 +1,664 @@
+#!/bin/sh
+
+test_description='git cat-file --batch-command with remote-object-info command'
+
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+
+. ./test-lib.sh
+. "$TEST_DIRECTORY"/lib-cat-file.sh
+
+hello_content="Hello World"
+hello_size=$(strlen "$hello_content")
+hello_oid=$(echo_without_newline "$hello_content" | git hash-object --stdin)
+
+# This is how we get 13:
+# 13 = <file mode> + <a_space> + <file name> + <a_null>, where
+# file mode is 100644, which is 6 characters;
+# file name is hello, which is 5 characters
+# a space is 1 character and a null is 1 character
+tree_size=$(($(test_oid rawsz) + 13))
+
+commit_message="Initial commit"
+
+# This is how we get 137:
+# 137 = <tree header> + <a_space> + <a newline> +
+# <Author line> + <a newline> +
+# <Committer line> + <a newline> +
+# <a newline> +
+# <commit message length>
+# An easier way to calculate is: 1. use `git cat-file commit <commit hash> | wc -c`,
+# to get 177, 2. then deduct 40 hex characters to get 137
+commit_size=$(($(test_oid hexsz) + 137))
+
+tag_header_without_oid="type blob
+tag hellotag
+tagger $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL>"
+tag_header_without_timestamp="object $hello_oid
+$tag_header_without_oid"
+tag_description="This is a tag"
+tag_content="$tag_header_without_timestamp 0 +0000
+
+$tag_description"
+
+tag_oid=$(echo_without_newline "$tag_content" | git hash-object -t tag --stdin -w)
+tag_size=$(strlen "$tag_content")
+
+set_transport_variables () {
+	hello_oid=$(echo_without_newline "$hello_content" | git hash-object --stdin)
+	tree_oid=$(git -C "$1" write-tree)
+	commit_oid=$(echo_without_newline "$commit_message" | git -C "$1" commit-tree $tree_oid)
+	tag_oid=$(echo_without_newline "$tag_content" | git -C "$1" hash-object -t tag --stdin -w)
+	tag_size=$(strlen "$tag_content")
+}
+
+# This section tests --batch-command with remote-object-info command
+# Since "%(objecttype)" is currently not supported by the command remote-object-info ,
+# the filters are set to "%(objectname) %(objectsize)" in some test cases.
+
+# Test --batch-command remote-object-info with 'git://' transport with
+# transfer.advertiseobjectinfo set to true, i.e. server has object-info capability
+. "$TEST_DIRECTORY"/lib-git-daemon.sh
+start_git_daemon --export-all --enable=receive-pack
+daemon_parent=$GIT_DAEMON_DOCUMENT_ROOT_PATH/parent
+
+test_expect_success 'create repo to be served by git-daemon' '
+	git init "$daemon_parent" &&
+	echo_without_newline "$hello_content" > $daemon_parent/hello &&
+	git -C "$daemon_parent" update-index --add hello &&
+	git -C "$daemon_parent" config transfer.advertiseobjectinfo true &&
+	git clone "$GIT_DAEMON_URL/parent" -n "$daemon_parent/daemon_client_empty"
+'
+
+test_expect_success 'batch-command remote-object-info git://' '
+	(
+		set_transport_variables "$daemon_parent" &&
+		cd "$daemon_parent/daemon_client_empty" &&
+
+		# These results prove remote-object-info can get object info from the remote
+		echo "$hello_oid $hello_size" >expect &&
+		echo "$tree_oid $tree_size" >>expect &&
+		echo "$commit_oid $commit_size" >>expect &&
+		echo "$tag_oid $tag_size" >>expect &&
+
+		# These results prove remote-object-info did not download objects from the remote
+		echo "$hello_oid missing" >>expect &&
+		echo "$tree_oid missing" >>expect &&
+		echo "$commit_oid missing" >>expect &&
+		echo "$tag_oid missing" >>expect &&
+
+		git cat-file --batch-command="%(objectname) %(objectsize)" >actual <<-EOF &&
+		remote-object-info "$GIT_DAEMON_URL/parent" $hello_oid
+		remote-object-info "$GIT_DAEMON_URL/parent" $tree_oid
+		remote-object-info "$GIT_DAEMON_URL/parent" $commit_oid
+		remote-object-info "$GIT_DAEMON_URL/parent" $tag_oid
+		info $hello_oid
+		info $tree_oid
+		info $commit_oid
+		info $tag_oid
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'batch-command remote-object-info git:// multiple sha1 per line' '
+	(
+		set_transport_variables "$daemon_parent" &&
+		cd "$daemon_parent/daemon_client_empty" &&
+
+		# These results prove remote-object-info can get object info from the remote
+		echo "$hello_oid $hello_size" >expect &&
+		echo "$tree_oid $tree_size" >>expect &&
+		echo "$commit_oid $commit_size" >>expect &&
+		echo "$tag_oid $tag_size" >>expect &&
+
+		# These results prove remote-object-info did not download objects from the remote
+		echo "$hello_oid missing" >>expect &&
+		echo "$tree_oid missing" >>expect &&
+		echo "$commit_oid missing" >>expect &&
+		echo "$tag_oid missing" >>expect &&
+
+		git cat-file --batch-command="%(objectname) %(objectsize)" >actual <<-EOF &&
+		remote-object-info "$GIT_DAEMON_URL/parent" $hello_oid $tree_oid $commit_oid $tag_oid
+		info $hello_oid
+		info $tree_oid
+		info $commit_oid
+		info $tag_oid
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'batch-command remote-object-info git:// default filter' '
+	(
+		set_transport_variables "$daemon_parent" &&
+		cd "$daemon_parent/daemon_client_empty" &&
+
+		echo "$hello_oid $hello_size" >expect &&
+		echo "$tree_oid $tree_size" >>expect &&
+		echo "$commit_oid $commit_size" >>expect &&
+		echo "$tag_oid $tag_size" >>expect &&
+		GIT_TRACE_PACKET=1 git cat-file --batch-command >actual <<-EOF &&
+		remote-object-info "$GIT_DAEMON_URL/parent" $hello_oid $tree_oid
+		remote-object-info "$GIT_DAEMON_URL/parent" $commit_oid $tag_oid
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'batch-command --buffer remote-object-info git://' '
+	(
+		set_transport_variables "$daemon_parent" &&
+		cd "$daemon_parent/daemon_client_empty" &&
+
+		# These results prove remote-object-info can get object info from the remote
+		echo "$hello_oid $hello_size" >expect &&
+		echo "$tree_oid $tree_size" >>expect &&
+		echo "$commit_oid $commit_size" >>expect &&
+		echo "$tag_oid $tag_size" >>expect &&
+
+		# These results prove remote-object-info did not download objects from the remote
+		echo "$hello_oid missing" >>expect &&
+		echo "$tree_oid missing" >>expect &&
+		echo "$commit_oid missing" >>expect &&
+		echo "$tag_oid missing" >>expect &&
+
+		git cat-file --batch-command="%(objectname) %(objectsize)" --buffer >actual <<-EOF &&
+		remote-object-info "$GIT_DAEMON_URL/parent" $hello_oid $tree_oid
+		remote-object-info "$GIT_DAEMON_URL/parent" $commit_oid $tag_oid
+		info $hello_oid
+		info $tree_oid
+		info $commit_oid
+		info $tag_oid
+		flush
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'batch-command -Z remote-object-info git:// default filter' '
+	(
+		set_transport_variables "$daemon_parent" &&
+		cd "$daemon_parent/daemon_client_empty" &&
+
+		printf "%s\0" "$hello_oid $hello_size" >expect &&
+		printf "%s\0" "$tree_oid $tree_size" >>expect &&
+		printf "%s\0" "$commit_oid $commit_size" >>expect &&
+		printf "%s\0" "$tag_oid $tag_size" >>expect &&
+
+		printf "%s\0" "$hello_oid missing" >>expect &&
+		printf "%s\0" "$tree_oid missing" >>expect &&
+		printf "%s\0" "$commit_oid missing" >>expect &&
+		printf "%s\0" "$tag_oid missing" >>expect &&
+
+		batch_input="remote-object-info $GIT_DAEMON_URL/parent $hello_oid $tree_oid
+remote-object-info $GIT_DAEMON_URL/parent $commit_oid $tag_oid
+info $hello_oid
+info $tree_oid
+info $commit_oid
+info $tag_oid
+" &&
+		echo_without_newline_nul "$batch_input" >commands_null_delimited &&
+
+		git cat-file --batch-command -Z < commands_null_delimited >actual &&
+		test_cmp expect actual
+	)
+'
+
+# Test --batch-command remote-object-info with 'git://' and
+# transfer.advertiseobjectinfo set to false, i.e. server does not have object-info capability
+test_expect_success 'batch-command remote-object-info git:// fails when transfer.advertiseobjectinfo=false' '
+	(
+		git -C "$daemon_parent" config transfer.advertiseobjectinfo false &&
+		set_transport_variables "$daemon_parent" &&
+
+		test_must_fail git cat-file --batch-command="%(objectname) %(objectsize)" 2>err <<-EOF &&
+		remote-object-info $GIT_DAEMON_URL/parent $hello_oid $tree_oid $commit_oid $tag_oid
+		EOF
+		test_grep "object-info capability is not enabled on the server" err &&
+
+		# revert server state back
+		git -C "$daemon_parent" config transfer.advertiseobjectinfo true
+
+	)
+'
+
+stop_git_daemon
+
+# Test --batch-command remote-object-info with 'file://' transport with
+# transfer.advertiseobjectinfo set to true, i.e. server has object-info capability
+# shellcheck disable=SC2016
+test_expect_success 'create repo to be served by file:// transport' '
+	git init server &&
+	git -C server config protocol.version 2 &&
+	git -C server config transfer.advertiseobjectinfo true &&
+	echo_without_newline "$hello_content" > server/hello &&
+	git -C server update-index --add hello &&
+	git clone -n "file://$(pwd)/server" file_client_empty
+'
+
+test_expect_success 'batch-command remote-object-info file://' '
+	(
+		set_transport_variables "server" &&
+		server_path="$(pwd)/server" &&
+		cd file_client_empty &&
+
+		# These results prove remote-object-info can get object info from the remote
+		echo "$hello_oid $hello_size" >expect &&
+		echo "$tree_oid $tree_size" >>expect &&
+		echo "$commit_oid $commit_size" >>expect &&
+		echo "$tag_oid $tag_size" >>expect &&
+
+		# These results prove remote-object-info did not download objects from the remote
+		echo "$hello_oid missing" >>expect &&
+		echo "$tree_oid missing" >>expect &&
+		echo "$commit_oid missing" >>expect &&
+		echo "$tag_oid missing" >>expect &&
+
+		git cat-file --batch-command="%(objectname) %(objectsize)" >actual <<-EOF &&
+		remote-object-info "file://${server_path}" $hello_oid
+		remote-object-info "file://${server_path}" $tree_oid
+		remote-object-info "file://${server_path}" $commit_oid
+		remote-object-info "file://${server_path}" $tag_oid
+		info $hello_oid
+		info $tree_oid
+		info $commit_oid
+		info $tag_oid
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'batch-command remote-object-info file:// multiple sha1 per line' '
+	(
+		set_transport_variables "server" &&
+		server_path="$(pwd)/server" &&
+		cd file_client_empty &&
+
+		# These results prove remote-object-info can get object info from the remote
+		echo "$hello_oid $hello_size" >expect &&
+		echo "$tree_oid $tree_size" >>expect &&
+		echo "$commit_oid $commit_size" >>expect &&
+		echo "$tag_oid $tag_size" >>expect &&
+
+		# These results prove remote-object-info did not download objects from the remote
+		echo "$hello_oid missing" >>expect &&
+		echo "$tree_oid missing" >>expect &&
+		echo "$commit_oid missing" >>expect &&
+		echo "$tag_oid missing" >>expect &&
+
+
+		git cat-file --batch-command="%(objectname) %(objectsize)" >actual <<-EOF &&
+		remote-object-info "file://${server_path}" $hello_oid $tree_oid $commit_oid $tag_oid
+		info $hello_oid
+		info $tree_oid
+		info $commit_oid
+		info $tag_oid
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'batch-command --buffer remote-object-info file://' '
+	(
+		set_transport_variables "server" &&
+		server_path="$(pwd)/server" &&
+		cd file_client_empty &&
+
+		# These results prove remote-object-info can get object info from the remote
+		echo "$hello_oid $hello_size" >expect &&
+		echo "$tree_oid $tree_size" >>expect &&
+		echo "$commit_oid $commit_size" >>expect &&
+		echo "$tag_oid $tag_size" >>expect &&
+
+		# These results prove remote-object-info did not download objects from the remote
+		echo "$hello_oid missing" >>expect &&
+		echo "$tree_oid missing" >>expect &&
+		echo "$commit_oid missing" >>expect &&
+		echo "$tag_oid missing" >>expect &&
+
+		git cat-file --batch-command="%(objectname) %(objectsize)" --buffer >actual <<-EOF &&
+		remote-object-info "file://${server_path}" $hello_oid $tree_oid
+		remote-object-info "file://${server_path}" $commit_oid $tag_oid
+		info $hello_oid
+		info $tree_oid
+		info $commit_oid
+		info $tag_oid
+		flush
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'batch-command remote-object-info file:// default filter' '
+	(
+		set_transport_variables "server" &&
+		server_path="$(pwd)/server" &&
+		cd file_client_empty &&
+
+		echo "$hello_oid $hello_size" >expect &&
+		echo "$tree_oid $tree_size" >>expect &&
+		echo "$commit_oid $commit_size" >>expect &&
+		echo "$tag_oid $tag_size" >>expect &&
+
+		git cat-file --batch-command >actual <<-EOF &&
+		remote-object-info "file://${server_path}" $hello_oid $tree_oid
+		remote-object-info "file://${server_path}" $commit_oid $tag_oid
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'batch-command -Z remote-object-info file:// default filter' '
+	(
+		set_transport_variables "server" &&
+		server_path="$(pwd)/server" &&
+		cd file_client_empty &&
+
+		printf "%s\0" "$hello_oid $hello_size" >expect &&
+		printf "%s\0" "$tree_oid $tree_size" >>expect &&
+		printf "%s\0" "$commit_oid $commit_size" >>expect &&
+		printf "%s\0" "$tag_oid $tag_size" >>expect &&
+
+		printf "%s\0" "$hello_oid missing" >>expect &&
+		printf "%s\0" "$tree_oid missing" >>expect &&
+		printf "%s\0" "$commit_oid missing" >>expect &&
+		printf "%s\0" "$tag_oid missing" >>expect &&
+
+		batch_input="remote-object-info \"file://${server_path}\" $hello_oid $tree_oid
+remote-object-info \"file://${server_path}\" $commit_oid $tag_oid
+info $hello_oid
+info $tree_oid
+info $commit_oid
+info $tag_oid
+" &&
+		echo_without_newline_nul "$batch_input" >commands_null_delimited &&
+
+		git cat-file --batch-command -Z < commands_null_delimited >actual &&
+		test_cmp expect actual
+	)
+'
+
+# Test --batch-command remote-object-info with 'file://' and
+# transfer.advertiseobjectinfo set to false, i.e. server does not have object-info capability
+test_expect_success 'batch-command remote-object-info file:// fails when transfer.advertiseobjectinfo=false' '
+	(
+		set_transport_variables "server" &&
+		server_path="$(pwd)/server" &&
+		git -C "${server_path}" config transfer.advertiseobjectinfo false &&
+
+		test_must_fail git cat-file --batch-command="%(objectname) %(objectsize)" 2>err <<-EOF &&
+		remote-object-info "file://${server_path}" $hello_oid $tree_oid $commit_oid $tag_oid
+		EOF
+		test_grep "object-info capability is not enabled on the server" err &&
+
+		# revert server state back
+		git -C "${server_path}" config transfer.advertiseobjectinfo true
+	)
+'
+
+# Test --batch-command remote-object-info with 'http://' transport with
+# transfer.advertiseobjectinfo set to true, i.e. server has object-info capability
+
+. "$TEST_DIRECTORY"/lib-httpd.sh
+start_httpd
+
+test_expect_success 'create repo to be served by http:// transport' '
+	git init "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+	git -C "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" config http.receivepack true &&
+	git -C "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" config transfer.advertiseobjectinfo true &&
+	echo_without_newline "$hello_content" > $HTTPD_DOCUMENT_ROOT_PATH/http_parent/hello &&
+	git -C "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" update-index --add hello &&
+	git clone "$HTTPD_URL/smart/http_parent" -n "$HTTPD_DOCUMENT_ROOT_PATH/http_client_empty"
+'
+
+test_expect_success 'batch-command remote-object-info http://' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_client_empty" &&
+
+		# These results prove remote-object-info can get object info from the remote
+		echo "$hello_oid $hello_size" >expect &&
+		echo "$tree_oid $tree_size" >>expect &&
+		echo "$commit_oid $commit_size" >>expect &&
+		echo "$tag_oid $tag_size" >>expect &&
+
+		# These results prove remote-object-info did not download objects from the remote
+		echo "$hello_oid missing" >>expect &&
+		echo "$tree_oid missing" >>expect &&
+		echo "$commit_oid missing" >>expect &&
+		echo "$tag_oid missing" >>expect &&
+
+		git cat-file --batch-command="%(objectname) %(objectsize)" >actual <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid
+		remote-object-info "$HTTPD_URL/smart/http_parent" $tree_oid
+		remote-object-info "$HTTPD_URL/smart/http_parent" $commit_oid
+		remote-object-info "$HTTPD_URL/smart/http_parent" $tag_oid
+		info $hello_oid
+		info $tree_oid
+		info $commit_oid
+		info $tag_oid
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'batch-command remote-object-info http:// one line' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_client_empty" &&
+
+		# These results prove remote-object-info can get object info from the remote
+		echo "$hello_oid $hello_size" >expect &&
+		echo "$tree_oid $tree_size" >>expect &&
+		echo "$commit_oid $commit_size" >>expect &&
+		echo "$tag_oid $tag_size" >>expect &&
+
+		# These results prove remote-object-info did not download objects from the remote
+		echo "$hello_oid missing" >>expect &&
+		echo "$tree_oid missing" >>expect &&
+		echo "$commit_oid missing" >>expect &&
+		echo "$tag_oid missing" >>expect &&
+
+		git cat-file --batch-command="%(objectname) %(objectsize)" >actual <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid $tree_oid $commit_oid $tag_oid
+		info $hello_oid
+		info $tree_oid
+		info $commit_oid
+		info $tag_oid
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'batch-command --buffer remote-object-info http://' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_client_empty" &&
+
+		# These results prove remote-object-info can get object info from the remote
+		echo "$hello_oid $hello_size" >expect &&
+		echo "$tree_oid $tree_size" >>expect &&
+		echo "$commit_oid $commit_size" >>expect &&
+		echo "$tag_oid $tag_size" >>expect &&
+
+		# These results prove remote-object-info did not download objects from the remote
+		echo "$hello_oid missing" >>expect &&
+		echo "$tree_oid missing" >>expect &&
+		echo "$commit_oid missing" >>expect &&
+		echo "$tag_oid missing" >>expect &&
+
+		git cat-file --batch-command="%(objectname) %(objectsize)" --buffer >actual <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid $tree_oid
+		remote-object-info "$HTTPD_URL/smart/http_parent" $commit_oid $tag_oid
+		info $hello_oid
+		info $tree_oid
+		info $commit_oid
+		info $tag_oid
+		flush
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'batch-command remote-object-info http:// default filter' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_client_empty" &&
+
+		echo "$hello_oid $hello_size" >expect &&
+		echo "$tree_oid $tree_size" >>expect &&
+		echo "$commit_oid $commit_size" >>expect &&
+		echo "$tag_oid $tag_size" >>expect &&
+
+		git cat-file --batch-command >actual <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid $tree_oid
+		remote-object-info "$HTTPD_URL/smart/http_parent" $commit_oid $tag_oid
+		EOF
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'batch-command -Z remote-object-info http:// default filter' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_client_empty" &&
+
+		printf "%s\0" "$hello_oid $hello_size" >expect &&
+		printf "%s\0" "$tree_oid $tree_size" >>expect &&
+		printf "%s\0" "$commit_oid $commit_size" >>expect &&
+		printf "%s\0" "$tag_oid $tag_size" >>expect &&
+
+		batch_input="remote-object-info $HTTPD_URL/smart/http_parent $hello_oid $tree_oid
+remote-object-info $HTTPD_URL/smart/http_parent $commit_oid $tag_oid
+" &&
+		echo_without_newline_nul "$batch_input" >commands_null_delimited &&
+
+		git cat-file --batch-command -Z < commands_null_delimited >actual &&
+		test_cmp expect actual
+	)
+'
+
+test_expect_success 'remote-object-info fails on unspported filter option (objectsize:disk)' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+
+		test_must_fail git cat-file --batch-command="%(objectsize:disk)" 2>err <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid
+		EOF
+		test_grep "%(objectsize:disk) is currently not supported with remote-object-info" err
+	)
+'
+
+test_expect_success 'remote-object-info fails on unspported filter option (deltabase)' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+
+		test_must_fail git cat-file --batch-command="%(deltabase)" 2>err <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid
+		EOF
+		test_grep "%(deltabase) is currently not supported with remote-object-info" err
+	)
+'
+
+test_expect_success 'remote-object-info fails on server with legacy protocol' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+
+		test_must_fail git -c protocol.version=0 cat-file --batch-command="%(objectname) %(objectsize)" 2>err <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid
+		EOF
+		test_grep "remote-object-info requires protocol v2" err
+	)
+'
+
+test_expect_success 'remote-object-info fails on server with legacy protocol with default filter' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+
+		test_must_fail git -c protocol.version=0 cat-file --batch-command 2>err <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid
+		EOF
+		test_grep "remote-object-info requires protocol v2" err
+	)
+'
+
+test_expect_success 'remote-object-info fails on malformed OID' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		malformed_object_id="this_id_is_not_valid" &&
+
+		test_must_fail git cat-file --batch-command="%(objectname) %(objectsize)" 2>err <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent" $malformed_object_id
+		EOF
+		test_grep "Not a valid object name '$malformed_object_id'" err
+	)
+'
+
+test_expect_success 'remote-object-info fails on malformed OID with default filter' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		malformed_object_id="this_id_is_not_valid" &&
+
+		test_must_fail git cat-file --batch-command 2>err <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent" $malformed_object_id
+		EOF
+		test_grep "Not a valid object name '$malformed_object_id'" err
+	)
+'
+
+test_expect_success 'remote-object-info fails on missing OID' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		git clone "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" missing_oid_repo &&
+		test_commit -C missing_oid_repo message1 c.txt &&
+		cd missing_oid_repo &&
+
+		object_id=$(git rev-parse message1:c.txt) &&
+		test_must_fail git cat-file --batch-command="%(objectname) %(objectsize)" 2>err <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent" $object_id
+		EOF
+		test_grep "object-info: server does not recognize object $object_id" err
+	)
+'
+
+test_expect_success 'remote-object-info fails on not providing OID' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+
+		test_must_fail git cat-file --batch-command="%(objectname) %(objectsize)" 2>err <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent"
+		EOF
+		test_grep "remote-object-info requires objects" err
+	)
+'
+
+
+# Test --batch-command remote-object-info with 'http://' transport and
+# transfer.advertiseobjectinfo set to false, i.e. server does not have object-info capability
+test_expect_success 'batch-command remote-object-info http:// fails when transfer.advertiseobjectinfo=false ' '
+	(
+		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
+		git -C "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" config transfer.advertiseobjectinfo false &&
+
+		test_must_fail git cat-file --batch-command="%(objectname) %(objectsize)" 2>err <<-EOF &&
+		remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid $tree_oid $commit_oid $tag_oid
+		EOF
+		test_grep "object-info capability is not enabled on the server" err &&
+
+		# revert server state back
+		git -C "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" config transfer.advertiseobjectinfo true
+	)
+'
+
+# DO NOT add non-httpd-specific tests here, because the last part of this
+# test script is only executed when httpd is available and enabled.
+
+test_done
diff --git a/transport.c b/transport.c
index 7d3246e12b..81faf8e748 100644
--- a/transport.c
+++ b/transport.c
@@ -470,8 +470,8 @@ static int fetch_refs_via_pack(struct transport *transport,
 	args.reject_shallow_remote = transport->smart_options->reject_shallow;
 	args.object_info = transport->smart_options->object_info;
 
-	if (transport->smart_options->object_info
-	    && transport->smart_options->object_info_oids->nr > 0) {
+	if (transport->smart_options->object_info &&
+	    transport->smart_options->object_info_oids->nr > 0) {
 		struct packet_reader reader;
 		struct object_info_args obj_info_args = { 0 };
 

-- 
2.54.0

^ permalink raw reply related

* [PATCH GSoC RFC v12 11/12] cat-file: validate remote atoms with allow_list
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20260608-ps-eric-work-rebase-v12-0-5338b766e658@gmail.com>

strstr() is not enough to validate the format placeholders in
remote-object-info causing two errors:

- Atoms recognized by expand_atom() but the remote doesn't returns 1, but
  data->type contains garbage causing segfault.
- expand_atom() returns 0 for unknown atoms, calling
  strbuf_expand_bad_format() which ends in die() blocking local queries
  if the same format is shared.

Add an allow_list with the supported atoms at the top of expand_atom().
In remote mode, unsupported atoms return 1 leaving the sb empty,
honoring how for-each-ref handles known but inapplicable atoms.

As extra safety, initialize data->type to OBJ_BAD and add a NULL check
for type_name() so uninitialized data doesn't cause segfault.

Update tests that expect previous die() behaviour to expect an empty
string and add an explicit test for empty string return on unknown
placeholder.

Update caveat behaviour documentation.

Mentored-by: Karthik Nayak <karthik.188@gmail.com>
Mentored-by: Chandra Pratap <chandrapratap3519@gmail.com>
Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 Documentation/git-cat-file.adoc        |  5 +++--
 builtin/cat-file.c                     | 41 +++++++++++++++++++++++++++-------
 t/t1017-cat-file-remote-object-info.sh | 28 +++++++++++++++++++----
 3 files changed, 60 insertions(+), 14 deletions(-)

diff --git a/Documentation/git-cat-file.adoc b/Documentation/git-cat-file.adoc
index aba20eb770..3b7a85b383 100644
--- a/Documentation/git-cat-file.adoc
+++ b/Documentation/git-cat-file.adoc
@@ -451,8 +451,9 @@ CAVEATS
 -------
 
 Note that since %(objecttype), %(objectsize:disk) and %(deltabase) are
-currently not supported by the `remote-object-info` command, we will raise
-an error and exit when they appear in the format string.
+currently not supported by the `remote-object-info` command, they will
+return an empty string for remote queries, matching how `for-each-ref`
+behaves for known but inapplicable placeholders.
 
 Note that the sizes of objects on disk are reported accurately, but care
 should be taken in drawing conclusions about which refs or objects are
diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index a14cfea815..1166a046b4 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -336,8 +336,18 @@ struct expand_data {
 	 * optimized out.
 	 */
 	unsigned skip_object_info : 1;
+
+	/*
+	 * Flags about when an object info is being fetched from remote.
+	 */
+	unsigned is_remote:1;
+};
+#define EXPAND_DATA_INIT  { .mode = S_IFINVALID, .type = OBJ_BAD }
+
+static const char *remote_object_info_atoms[] = {
+	"objectname",
+	"objectsize",
 };
-#define EXPAND_DATA_INIT  { .mode = S_IFINVALID }
 
 static int is_atom(const char *atom, const char *s, int slen)
 {
@@ -348,14 +358,31 @@ static int is_atom(const char *atom, const char *s, int slen)
 static int expand_atom(struct strbuf *sb, const char *atom, int len,
 		       struct expand_data *data)
 {
+	if (data->is_remote) {
+		size_t i, allowed_nr = ARRAY_SIZE(remote_object_info_atoms);
+		for (i = 0; i < allowed_nr; i++)
+			if (is_atom(remote_object_info_atoms[i], atom, len))
+				break;
+
+		/*
+		 * On remote, skip unsupported atoms returning an empty sb,
+		 * honoring how for-each-ref handles known but inapplicable
+		 * atoms (e.g. %(tagger)).
+		 */
+		if (i == allowed_nr)
+			return 1;
+	}
+
 	if (is_atom("objectname", atom, len)) {
 		if (!data->mark_query)
 			strbuf_addstr(sb, oid_to_hex(&data->oid));
 	} else if (is_atom("objecttype", atom, len)) {
-		if (data->mark_query)
+		if (data->mark_query) {
 			data->info.typep = &data->type;
-		else
-			strbuf_addstr(sb, type_name(data->type));
+		} else {
+			const char *t = type_name(data->type);
+			strbuf_addstr(sb, t ? t : "");
+		}
 	} else if (is_atom("objectsize", atom, len)) {
 		if (data->mark_query)
 			data->info.sizep = &data->size;
@@ -699,10 +726,6 @@ static int get_remote_info(struct batch_options *opt,
 	gtransport->smart_options->object_info = 1;
 	gtransport->smart_options->object_info_oids = object_info_oids;
 
-	/* 'objectsize' is the only option currently supported */
-	if (!strstr(opt->format, "%(objectsize)"))
-		die(_("%s is currently not supported with remote-object-info"), opt->format);
-
 	string_list_append(&object_info_options, "size");
 
 	if (object_info_options.nr > 0) {
@@ -832,7 +855,9 @@ static void parse_cmd_remote_object_info(struct batch_options *opt,
 			 */
 			data->size = *remote_object_info[i].sizep;
 			opt->batch_mode = BATCH_MODE_INFO;
+			data->is_remote = 1;
 			batch_object_write(argv[i + 1], output, opt, data, NULL, 0);
+			data->is_remote = 0;
 		}
 	}
 	data->skip_object_info = 0;
diff --git a/t/t1017-cat-file-remote-object-info.sh b/t/t1017-cat-file-remote-object-info.sh
index 5c8c07b0cf..0a78aabf3b 100755
--- a/t/t1017-cat-file-remote-object-info.sh
+++ b/t/t1017-cat-file-remote-object-info.sh
@@ -205,6 +205,22 @@ info $tag_oid
 	)
 '
 
+# This tests depends on %(objecttype) not being supported yet, once supported
+# it needs to be updated.
+test_expect_success 'unsupported placeholder on remote returns empty string' '
+	(
+		set_transport_variables "$daemon_parent" &&
+		cd "$daemon_parent/daemon_client_empty" &&
+
+		echo "" >expect &&
+
+		git cat-file --batch-command="%(objecttype)" >actual <<-EOF &&
+		remote-object-info "$GIT_DAEMON_URL/parent" $hello_oid
+		EOF
+		test_cmp expect actual
+	)
+'
+
 # Test --batch-command remote-object-info with 'git://' and
 # transfer.advertiseobjectinfo set to false, i.e. server does not have object-info capability
 test_expect_success 'batch-command remote-object-info git:// fails when transfer.advertiseobjectinfo=false' '
@@ -544,10 +560,12 @@ test_expect_success 'remote-object-info fails on unspported filter option (objec
 		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
 		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
 
-		test_must_fail git cat-file --batch-command="%(objectsize:disk)" 2>err <<-EOF &&
+		echo "$hello_oid " >expect &&
+
+		git cat-file --batch-command="%(objectname) %(objectsize:disk)" >actual <<-EOF &&
 		remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid
 		EOF
-		test_grep "%(objectsize:disk) is currently not supported with remote-object-info" err
+		test_cmp expect actual
 	)
 '
 
@@ -556,10 +574,12 @@ test_expect_success 'remote-object-info fails on unspported filter option (delta
 		set_transport_variables "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
 		cd "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" &&
 
-		test_must_fail git cat-file --batch-command="%(deltabase)" 2>err <<-EOF &&
+		echo "" >expect &&
+
+		git cat-file --batch-command="%(deltabase)" >actual <<-EOF &&
 		remote-object-info "$HTTPD_URL/smart/http_parent" $hello_oid
 		EOF
-		test_grep "%(deltabase) is currently not supported with remote-object-info" err
+		test_cmp expect actual
 	)
 '
 

-- 
2.54.0

^ permalink raw reply related

* [PATCH GSoC RFC v12 12/12] cat-file: make remote-object-info allow-list dynamic
From: Pablo Sabater @ 2026-06-08 10:14 UTC (permalink / raw)
  To: eric.peijian
  Cc: calvinwan, chriscool, git, jltobler, jonathantanmy, karthik.188,
	toon, chandrapratap3519, Pablo Sabater
In-Reply-To: <20260608-ps-eric-work-rebase-v12-0-5338b766e658@gmail.com>

The static allow-list in expand_atom() is hardcoded to only allow
"objectname" and "objectsize" for remote queries. This works because
up to this point all servers will either support object-info with name
and size or they do not support them at all, but we cannot expect that
in a future different servers with different git versions to have the
same object-info capabilities. Therefore, the allow_list needs to be
dynamic depending on what does the server advertise.

The client will now:

1. Request the protocol option that the placeholder refers to (i.e.
   "size" when "%(objectsize)").

2. Filters the request in fetch_object_info() dropping any option that
   the server does not advertise.

3. After the fetching, the options that haven't been dropped are the ones
   fetched and supported by the server, these supported options are
   mapped and remote_allowed_atoms is populated with the placeholders.

4. expand_atom() checks remote_allowed_atoms with the same behaviour as
   the static allow_list had.

Move object_info_options out of get_remote_info so the caller which has
data can select what options will be requested instead of requesting
always size.
Move batch_object_write() out so there will always be an output even if
all the placeholders are not supported by the server (returns an empty
line).

Include "type" in the object_info_options so once the server supports
it, the clients know already how to request it.

Mentored-by: Karthik Nayak <karthik.188@gmail.com>
Mentored-by: Chandra Pratap <chandrapratap3519@gmail.com>
Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
 builtin/cat-file.c  | 85 ++++++++++++++++++++++++++++++++---------------------
 fetch-object-info.c |  6 ++++
 2 files changed, 58 insertions(+), 33 deletions(-)

diff --git a/builtin/cat-file.c b/builtin/cat-file.c
index 1166a046b4..055991b5af 100644
--- a/builtin/cat-file.c
+++ b/builtin/cat-file.c
@@ -341,13 +341,10 @@ struct expand_data {
 	 * Flags about when an object info is being fetched from remote.
 	 */
 	unsigned is_remote:1;
-};
-#define EXPAND_DATA_INIT  { .mode = S_IFINVALID, .type = OBJ_BAD }
 
-static const char *remote_object_info_atoms[] = {
-	"objectname",
-	"objectsize",
+	struct string_list remote_allowed_atoms;
 };
+#define EXPAND_DATA_INIT  { .mode = S_IFINVALID, .type = OBJ_BAD, .remote_allowed_atoms = STRING_LIST_INIT_NODUP }
 
 static int is_atom(const char *atom, const char *s, int slen)
 {
@@ -359,17 +356,11 @@ static int expand_atom(struct strbuf *sb, const char *atom, int len,
 		       struct expand_data *data)
 {
 	if (data->is_remote) {
-		size_t i, allowed_nr = ARRAY_SIZE(remote_object_info_atoms);
-		for (i = 0; i < allowed_nr; i++)
-			if (is_atom(remote_object_info_atoms[i], atom, len))
+		size_t i;
+		for (i = 0; i < data->remote_allowed_atoms.nr; i++)
+			if (is_atom(data->remote_allowed_atoms.items[i].string, atom, len))
 				break;
-
-		/*
-		 * On remote, skip unsupported atoms returning an empty sb,
-		 * honoring how for-each-ref handles known but inapplicable
-		 * atoms (e.g. %(tagger)).
-		 */
-		if (i == allowed_nr)
+		if (i == data->remote_allowed_atoms.nr)
 			return 1;
 	}
 
@@ -686,12 +677,12 @@ static int get_remote_info(struct batch_options *opt,
 			   int argc,
 			   const char **argv,
 			   struct object_info **remote_object_info,
-			   struct oid_array *object_info_oids)
+			   struct oid_array *object_info_oids,
+			   struct string_list *object_info_options)
 {
 	int retval = 0;
 	struct remote *remote = NULL;
 	struct object_id oid;
-	struct string_list object_info_options = STRING_LIST_INIT_NODUP;
 	static struct transport *gtransport;
 
 	/*
@@ -726,15 +717,12 @@ static int get_remote_info(struct batch_options *opt,
 	gtransport->smart_options->object_info = 1;
 	gtransport->smart_options->object_info_oids = object_info_oids;
 
-	string_list_append(&object_info_options, "size");
-
-	if (object_info_options.nr > 0) {
-		gtransport->smart_options->object_info_options = &object_info_options;
+	if (object_info_options->nr > 0) {
+		gtransport->smart_options->object_info_options = object_info_options;
 		gtransport->smart_options->object_info_data = *remote_object_info;
 		retval = transport_fetch_refs(gtransport, NULL);
 	}
 cleanup:
-	string_list_clear(&object_info_options, 0);
 	transport_disconnect(gtransport);
 	return retval;
 }
@@ -820,6 +808,21 @@ static void parse_cmd_mailmap(struct batch_options *opt UNUSED,
 		load_mailmap();
 }
 
+struct protocol_placeholder_entry {
+	const char *option;
+	const char *atom;
+};
+
+static const struct protocol_placeholder_entry remote_atom_map[] = {
+	{"size", "objectsize"},
+	{"type", "objecttype"},
+	/*
+	 * Add new protocol options here. Even if the server doesn't support
+	 * them the allow_list will drop them if the server doesn't advertise
+	 * them.
+	 */
+};
+
 static void parse_cmd_remote_object_info(struct batch_options *opt,
 					 const char *line, struct strbuf *output,
 					 struct expand_data *data)
@@ -829,6 +832,7 @@ static void parse_cmd_remote_object_info(struct batch_options *opt,
 	char *line_to_split;
 	static struct object_info *remote_object_info;
 	static struct oid_array object_info_oids = OID_ARRAY_INIT;
+	struct string_list object_info_options = STRING_LIST_INIT_NODUP;
 
 	if (strlen(line) >= MAX_REMOTE_OBJ_INFO_LINE)
 		die(_("remote-object-info command too long"));
@@ -841,30 +845,44 @@ static void parse_cmd_remote_object_info(struct batch_options *opt,
 		die(_("remote-object-info supports at most %d objects"),
 		    MAX_ALLOWED_OBJ_LIMIT);
 
+	if (data->info.sizep)
+		string_list_append(&object_info_options, "size");
+	if (data->info.typep)
+		string_list_append(&object_info_options, "type");
+
 	if (get_remote_info(opt, count, argv, &remote_object_info,
-			    &object_info_oids))
+			    &object_info_oids, &object_info_options))
 		goto cleanup;
 
+	string_list_clear(&data->remote_allowed_atoms, 0);
+	string_list_append(&data->remote_allowed_atoms, "objectname");
+	for (size_t i = 0; i < ARRAY_SIZE(remote_atom_map); i++)
+		if (unsorted_string_list_has_string(&object_info_options, remote_atom_map[i].option))
+			string_list_append(&data->remote_allowed_atoms,
+					   remote_atom_map[i].atom);
+
 	data->skip_object_info = 1;
 	for (size_t i = 0; i < object_info_oids.nr; i++) {
 		data->oid = object_info_oids.oid[i];
-		if (remote_object_info[i].sizep) {
-			/*
-			 * When reaching here, it means remote-object-info can retrieve
-			 * information from server without downloading them.
-			 */
+		/*
+		 * When reaching here, it means remote-object-info can retrieve
+		 * information from server without downloading them.
+		 */
+		if (remote_object_info[i].sizep)
 			data->size = *remote_object_info[i].sizep;
-			opt->batch_mode = BATCH_MODE_INFO;
-			data->is_remote = 1;
-			batch_object_write(argv[i + 1], output, opt, data, NULL, 0);
-			data->is_remote = 0;
-		}
+		if (remote_object_info[i].typep)
+			data->type = *remote_object_info[i].typep;
+		opt->batch_mode = BATCH_MODE_INFO;
+		data->is_remote = 1;
+		batch_object_write(argv[i + 1], output, opt, data, NULL, 0);
+		data->is_remote = 0;
 	}
 	data->skip_object_info = 0;
 
 cleanup:
 	for (size_t i = 0; i < object_info_oids.nr; i++)
 		free_object_info_contents(&remote_object_info[i]);
+	string_list_clear(&object_info_options, 0);
 	free(line_to_split);
 	free(argv);
 	free(remote_object_info);
@@ -1177,6 +1195,7 @@ static int batch_objects(struct batch_options *opt)
  cleanup:
 	strbuf_release(&input);
 	strbuf_release(&output);
+	string_list_clear(&data.remote_allowed_atoms, 0);
 	warn_on_object_refname_ambiguity = save_warning;
 	return retval;
 }
diff --git a/fetch-object-info.c b/fetch-object-info.c
index 51a898430d..425929a269 100644
--- a/fetch-object-info.c
+++ b/fetch-object-info.c
@@ -39,6 +39,12 @@ int fetch_object_info(const enum protocol_version version, struct object_info_ar
 	case protocol_v2:
 		if (!server_supports_v2("object-info"))
 			die(_("object-info capability is not enabled on the server"));
+
+		for (int i = args->object_info_options->nr - 1; i >= 0; i--)
+			if (!server_supports_feature("object-info",
+						     args->object_info_options->items[i].string, 0))
+				unsorted_string_list_delete_item(args->object_info_options, i, 0);
+
 		send_object_info_request(fd_out, args);
 		break;
 	case protocol_v1:

-- 
2.54.0

^ permalink raw reply related

* [PATCH v3 0/9] builtin/history: introduce "drop" subcommand
From: Patrick Steinhardt @ 2026-06-08 10:23 UTC (permalink / raw)
  To: git; +Cc: Pablo Sabater, Junio C Hamano, Kristoffer Haugsbakk, Phillip Wood
In-Reply-To: <20260601-b4-pks-history-drop-v1-0-643e32340d55@pks.im>

Hi,

this small patch series introduces the new "drop" subcommand for
git-history(1). As a reader might guess, the command does exactly that:
given a commit, it will drop that commit from the commit history and
replay descendant branches on top of it.

Changes in v3:
  - Fix commit message typos.
  - Make `update_orig_head` and `skip_ref_updates` mutually exclusive.
  - Use fancy revisions to specify the commit to drop in the example
    section.
  - Detect conflicting changes in the index/working tree in dry-run
    mode.
  - Consistently use a subshell.
  - Rename `RESET_HEAD_ORIG_HEAD` to `RESET_HEAD_UPDATE_ORIG_HEAD`.
  - 
  - Link to v2: https://patch.msgid.link/20260603-b4-pks-history-drop-v2-0-742cb5b5176d@pks.im

Changes in v2:
  - Reworked `update_worktree()` to use `reset_head()`, which required a
    bunch of changes to `reset_head()`.
  - Consistently mention the commit that cannot be dropped as part of
    error messages.
  - Adapt error message to not use backticks anymore.
  - Drop redundant "--graph" flag in a test helper.
  - Link to v1: https://patch.msgid.link/20260601-b4-pks-history-drop-v1-0-643e32340d55@pks.im

Thanks!

Patrick

---
Patrick Steinhardt (9):
      read-cache: split out function to drop unmerged entries to stage 0
      reset: drop `USE_THE_REPOSITORY_VARIABLE`
      reset: modernize flags passed to `reset_head()`
      reset: introduce dry-run mode
      reset: introduce ability to skip reference updates
      reset: allow the caller to specify the current HEAD object
      reset: stop assuming that the caller passes in a clean index
      builtin/history: split handling of ref updates into two phases
      builtin/history: implement "drop" subcommand

 Documentation/git-history.adoc |  38 ++-
 builtin/history.c              | 289 +++++++++++++++++++---
 builtin/rebase.c               |   2 +-
 read-cache-ll.h                |   1 +
 read-cache.c                   |  12 +-
 reset.c                        |  91 ++++---
 reset.h                        |  44 +++-
 sequencer.c                    |   2 +-
 t/meson.build                  |   1 +
 t/t3454-history-drop.sh        | 537 +++++++++++++++++++++++++++++++++++++++++
 10 files changed, 929 insertions(+), 88 deletions(-)

Range-diff versus v2:

 1:  a93e804936 =  1:  41a723b3d0 read-cache: split out function to drop unmerged entries to stage 0
 2:  d8f39e7dc4 =  2:  db850730ef reset: drop `USE_THE_REPOSITORY_VARIABLE`
 3:  fdec5a57b4 !  3:  bd18736141 reset: modernize flags passed to `reset_head()`
    @@ builtin/rebase.c: int cmd_rebase(int argc,
      	ropts.oid = &options.onto->object.oid;
      	ropts.orig_head = &options.orig_head->object.oid;
     -	ropts.flags = RESET_HEAD_DETACH | RESET_ORIG_HEAD |
    -+	ropts.flags = RESET_HEAD_DETACH | RESET_HEAD_ORIG_HEAD |
    ++	ropts.flags = RESET_HEAD_DETACH | RESET_HEAD_UPDATE_ORIG_HEAD |
      			RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
      	ropts.head_msg = msg.buf;
      	ropts.default_reflog_action = options.reflog_action;
    @@ reset.c: static int update_refs(struct repository *repo,
      	unsigned detach_head = opts->flags & RESET_HEAD_DETACH;
      	unsigned run_hook = opts->flags & RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
     -	unsigned update_orig_head = opts->flags & RESET_ORIG_HEAD;
    -+	unsigned update_orig_head = opts->flags & RESET_HEAD_ORIG_HEAD;
    ++	unsigned update_orig_head = opts->flags & RESET_HEAD_UPDATE_ORIG_HEAD;
      	const struct object_id *orig_head = opts->orig_head;
      	const char *switch_to_branch = opts->branch;
      	const char *reflog_branch = opts->branch_msg;
    @@ reset.c: int reset_head(struct repository *r, const struct reset_head_opts *opts
      	unsigned reset_hard = opts->flags & RESET_HEAD_HARD;
      	unsigned refs_only = opts->flags & RESET_HEAD_REFS_ONLY;
     -	unsigned update_orig_head = opts->flags & RESET_ORIG_HEAD;
    -+	unsigned update_orig_head = opts->flags & RESET_HEAD_ORIG_HEAD;
    ++	unsigned update_orig_head = opts->flags & RESET_HEAD_UPDATE_ORIG_HEAD;
      	struct object_id *head = NULL, head_oid;
      	struct tree_desc desc[2] = { { NULL }, { NULL } };
      	struct lock_file lock = LOCK_INIT;
    @@ reset.h
     +	RESET_HEAD_REFS_ONLY = (1 << 3),
     +
     +	/* Update ORIG_HEAD as well as HEAD */
    -+	RESET_HEAD_ORIG_HEAD = (1 << 4),
    ++	RESET_HEAD_UPDATE_ORIG_HEAD = (1 << 4),
     +};
      
      struct reset_head_opts {
    @@ reset.h: struct reset_head_opts {
      	/*
      	 * Optional reflog message for ORIG_HEAD, if this omitted and flags
     -	 * contains RESET_ORIG_HEAD then default_reflog_action must be given.
    -+	 * contains RESET_HEAD_ORIG_HEAD then default_reflog_action must be given.
    ++	 * contains RESET_HEAD_UPDATE_ORIG_HEAD then default_reflog_action must be given.
      	 */
      	const char *orig_head_msg;
      	/*
    @@ sequencer.c: static int checkout_onto(struct repository *r, struct replay_opts *
      		.oid = onto,
      		.orig_head = orig_head,
     -		.flags = RESET_HEAD_DETACH | RESET_ORIG_HEAD |
    -+		.flags = RESET_HEAD_DETACH | RESET_HEAD_ORIG_HEAD |
    ++		.flags = RESET_HEAD_DETACH | RESET_HEAD_UPDATE_ORIG_HEAD |
      				RESET_HEAD_RUN_POST_CHECKOUT_HOOK,
      		.head_msg = reflog_message(opts, "start", "checkout %s",
      					   onto_name),
 4:  3af7c9a4fd !  4:  8c79e56076 reset: introduce dry-run mode
    @@ Metadata
      ## Commit message ##
         reset: introduce dry-run mode
     
    -    In a subsequent commit we'll add add another caller to `reset_head()`
    -    that wants to perform a dry-run check of whether it would be possible to
    -    udpate the index and working tree when moving to a new commit. Introduce
    +    In a subsequent commit we'll add another caller to `reset_head()` that
    +    wants to perform a dry-run check of whether it would be possible to
    +    update the index and working tree when moving to a new commit. Introduce
         a new flag that lets the caller perform this operation.
     
         Signed-off-by: Patrick Steinhardt <ps@pks.im>
    @@ reset.c
     @@ reset.c: int reset_head(struct repository *r, const struct reset_head_opts *opts)
      	unsigned reset_hard = opts->flags & RESET_HEAD_HARD;
      	unsigned refs_only = opts->flags & RESET_HEAD_REFS_ONLY;
    - 	unsigned update_orig_head = opts->flags & RESET_HEAD_ORIG_HEAD;
    + 	unsigned update_orig_head = opts->flags & RESET_HEAD_UPDATE_ORIG_HEAD;
     +	unsigned dry_run = opts->flags & RESET_HEAD_DRY_RUN;
      	struct object_id *head = NULL, head_oid;
      	struct tree_desc desc[2] = { { NULL }, { NULL } };
    @@ reset.h
     @@ reset.h: enum reset_head_flags {
      
      	/* Update ORIG_HEAD as well as HEAD */
    - 	RESET_HEAD_ORIG_HEAD = (1 << 4),
    + 	RESET_HEAD_UPDATE_ORIG_HEAD = (1 << 4),
     +
     +	/*
     +	 * Perform a dry-run by performing the operation without updating
 5:  31d1ff1d4c !  5:  c112fbbd14 reset: introduce ability to skip reference updates
    @@ Commit message
      ## reset.c ##
     @@ reset.c: int reset_head(struct repository *r, const struct reset_head_opts *opts)
      	unsigned refs_only = opts->flags & RESET_HEAD_REFS_ONLY;
    - 	unsigned update_orig_head = opts->flags & RESET_HEAD_ORIG_HEAD;
    + 	unsigned update_orig_head = opts->flags & RESET_HEAD_UPDATE_ORIG_HEAD;
      	unsigned dry_run = opts->flags & RESET_HEAD_DRY_RUN;
     +	unsigned skip_ref_updates = opts->flags & RESET_HEAD_SKIP_REF_UPDATES;
      	struct object_id *head = NULL, head_oid;
    @@ reset.c: int reset_head(struct repository *r, const struct reset_head_opts *opts
      	if (opts->branch_msg && !opts->branch)
      		BUG("branch reflog message given without a branch");
      
    -+	if (skip_ref_updates && (opts->branch || refs_only))
    ++	if (skip_ref_updates && (opts->branch || refs_only || update_orig_head))
     +		BUG("asked to perform ref updates and skip them at the same time");
     +
      	if (!refs_only && !dry_run && repo_hold_locked_index(r, &lock, LOCK_REPORT_ON_ERROR) < 0) {
 6:  21b2d4d281 =  6:  9550257dd1 reset: allow the caller to specify the current HEAD object
 7:  7c032ca1e3 =  7:  8a3d517020 reset: stop assuming that the caller passes in a clean index
 8:  fcd4479178 =  8:  a09be2ffc0 builtin/history: split handling of ref updates into two phases
 9:  6b1c17a8df !  9:  682b11af93 builtin/history: implement "drop" subcommand
    @@ Documentation/git-history.adoc: The staged addition of `unrelated.txt` has been
     +def5678 second
     +ghi9012 first
     +
    -+$ git history drop def5678
    ++$ git history drop 'main^{/second}'
     +
     +$ git log --oneline
     +jkl3456 (HEAD -> main) third
    @@ builtin/history.c: static int cmd_history_split(int argc,
     +	 * inconsistent repository state. So we first perform a dry-run merge
     +	 * here before updating refs.
     +	 */
    -+	if (!dry_run && !is_bare_repository()) {
    ++	if (!is_bare_repository()) {
     +		ret = find_head_tree_change(repo, &result, &old_head,
     +					    &new_head, &head_moves);
     +		if (ret < 0)
    @@ builtin/history.c: static int cmd_history_split(int argc,
     +		goto out;
     +	}
     +
    -+	if (head_moves && update_worktree(repo, old_head, new_head, false) < 0) {
    ++	if (!dry_run && head_moves && update_worktree(repo, old_head, new_head, false) < 0) {
     +		ret = error(_("could not update working tree to new commit %s"),
     +			    oid_to_hex(&new_head->object.oid));
     +		goto out;
    @@ t/t3454-history-drop.sh (new)
     +test_expect_success 'errors with invalid --empty= value' '
     +	test_when_finished "rm -rf repo" &&
     +	git init repo &&
    -+	test_commit -C repo initial &&
    -+	test_commit -C repo second &&
    -+	test_must_fail git -C repo history drop --empty=bogus HEAD 2>err &&
    -+	test_grep "unrecognized.*--empty.*bogus" err
    ++	(
    ++		cd repo &&
    ++		test_commit initial &&
    ++		test_commit second &&
    ++		test_must_fail git history drop --empty=bogus HEAD 2>err &&
    ++		test_grep "unrecognized.*--empty.*bogus" err
    ++	)
     +'
     +
     +test_expect_success 'drops a commit in the middle and replays descendants' '
    @@ t/t3454-history-drop.sh (new)
     +	)
     +'
     +
    ++test_expect_success '--dry-run detects conflicts with modified working tree' '
    ++	test_when_finished "rm -rf repo" &&
    ++	git init repo --initial-branch=main &&
    ++	(
    ++		cd repo &&
    ++		test_commit first &&
    ++		test_commit second modify-me &&
    ++		echo modified >modify-me &&
    ++
    ++		git refs list >refs-expect &&
    ++		git diff >diff-expect &&
    ++		test_must_fail git history drop --dry-run HEAD 2>err &&
    ++		test_grep "dropping this commit would overwrite local changes" err &&
    ++		git diff >diff-actual &&
    ++		git refs list >refs-actual &&
    ++
    ++		test_cmp diff-expect diff-actual &&
    ++		test_cmp refs-expect refs-actual
    ++	)
    ++'
    ++
     +test_expect_success '--update-refs=head updates only HEAD' '
     +	test_when_finished "rm -rf repo" &&
     +	git init repo --initial-branch=main &&

---
base-commit: 1666c1265231b0bc5f613fbbf3f0a9896cdef76e
change-id: 20260601-b4-pks-history-drop-28f6c6399e7b


^ permalink raw reply

* [PATCH v3 1/9] read-cache: split out function to drop unmerged entries to stage 0
From: Patrick Steinhardt @ 2026-06-08 10:23 UTC (permalink / raw)
  To: git; +Cc: Pablo Sabater, Junio C Hamano, Kristoffer Haugsbakk, Phillip Wood
In-Reply-To: <20260608-b4-pks-history-drop-v3-0-84ca8e43e937@pks.im>

In `repo_read_index_unmerged()` we read the index and then drop any
unmerged entries to stage 0. In a subsequent commit we'll want to
perform this operation on arbitrary indexes, not only the one of the
given repository.

Prepare for this by splitting out the functionality into a new function
that can act on an arbitrary index.

While at it, fix a signedness mismatch when iterating through the index
cache entries.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 read-cache-ll.h |  1 +
 read-cache.c    | 12 +++++++-----
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/read-cache-ll.h b/read-cache-ll.h
index 2c8b4b21b1..71b87615eb 100644
--- a/read-cache-ll.h
+++ b/read-cache-ll.h
@@ -309,6 +309,7 @@ int write_locked_index(struct index_state *, struct lock_file *lock, unsigned fl
 void discard_index(struct index_state *);
 void move_index_extensions(struct index_state *dst, struct index_state *src);
 int unmerged_index(const struct index_state *);
+int index_state_unmerged_to_stage0(struct index_state *istate);
 
 /**
  * Returns 1 if istate differs from tree, 0 otherwise.  If tree is NULL,
diff --git a/read-cache.c b/read-cache.c
index 21829102ae..799a5bc719 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -3403,13 +3403,15 @@ int write_locked_index(struct index_state *istate, struct lock_file *lock,
  */
 int repo_read_index_unmerged(struct repository *repo)
 {
-	struct index_state *istate;
-	int i;
+	repo_read_index(repo);
+	return index_state_unmerged_to_stage0(repo->index);
+}
+
+int index_state_unmerged_to_stage0(struct index_state *istate)
+{
 	int unmerged = 0;
 
-	repo_read_index(repo);
-	istate = repo->index;
-	for (i = 0; i < istate->cache_nr; i++) {
+	for (unsigned int i = 0; i < istate->cache_nr; i++) {
 		struct cache_entry *ce = istate->cache[i];
 		struct cache_entry *new_ce;
 		int len;

-- 
2.54.0.1136.gdb2ca164c4.dirty


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