Re: [PATCH v3 2/2] commit: allow -c/-C for all kinds of --fixup

[Phillip Wood <phillip.wood123@gmail.com>]

Hi Erik

On 22/09/2026 14:04, erik@cervined.in wrote:
> From: Erik Cervin-Edin <erik@cervined.in>
> 
> The fixup code path in prepare_to_commit() only knows how to take a
> message body from -m or -F.  Now that the previous commit allows -m and
> -F for all --fixup variations, -c/-C are the odd ones out.
> 
> Teach the fixup path to look up the ref given to -c/-C and seed its
> message when preparing to amend the commit, mirroring what --fixup=amend
> does when no message source is given.  With this in place, -m/-F/-c/-C
> all behave consistently across the plain, amend, and reword --fixup
> forms.
> 
> The incompatibility check grouping -C, -c, and --fixup can go away
> entirely, as -C and -c are already rejected together by the check that
> groups them with -m and -F.

I'm less convinced about there being much use for combining "--fixup" 
with "-C" but I don't see any reason to prevent it.

> @@ -863,6 +863,11 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
>   		} else if (logfile) {
>   			if (strbuf_read_file(&sb, logfile, 0) < 0)
>   				die_errno(_("could not read log file '%s'"), logfile);
> +		} else if (use_message) {

by the time we get here we've copied edit_message into use_message if 
"-c" was given so this covers "-C" and "-c".

> +			struct commit *c = lookup_commit_reference_by_name(use_message);
> +			if (!c)
> +				die(_("could not lookup commit '%s'"), use_message);
> +			prepare_amend_commit(c, &sb, &ctx);

> diff --git a/t/t7500-commit-template-squash-signoff.sh b/t/t7500-commit-template-squash-signoff.sh
> index 9b2ecb1356..de3221ea52 100755
> --- a/t/t7500-commit-template-squash-signoff.sh
> +++ b/t/t7500-commit-template-squash-signoff.sh
> @@ -492,6 +492,62 @@ test_expect_success 'commit --fixup works with -F' '
>   	EOF
>   '
>   
> +test_expect_success 'commit --fixup works with -C' '
> +	commit_for_rebase_autosquash_setup &&
> +	git commit --fixup HEAD~ -C HEAD &&

It would be nice to see

	GIT_EDITOR=false git commit --fixup HEAD~ -C HEAD

so that we check the editor is not invoked.

> +	test_commit_message HEAD <<-EOF
> +	fixup! $(git log -1 --format=%s HEAD~2)
> +
> +	$(get_commit_msg HEAD~)
> +	EOF
> +'
> +
> +test_expect_success 'commit --fixup=amend: works with -c' '
> +	commit_for_rebase_autosquash_setup &&
> +	test_set_editor : &&

Most of the tests in this file correctly use a subshell when setting the 
editor so that they do not affect subsequent tests. It would be nice to 
check that the editor actually ran.

	GIT_EDITOR="echo edited >>" git commit ---fixup=amend:HEAD -c HEAD~ &&

Thanks

Phillip

> +	git commit --fixup=amend:HEAD -c HEAD~ &&
> +	test_commit_message HEAD <<-EOF
> +	amend! intermediate commit
> +
> +	target message subject line
> +
> +	target message body line 1
> +	target message body line 2
> +	EOF
> +'
> +
> +test_expect_success 'commit --fixup=amend:HEAD with -C HEAD and without have the same message' '
> +	commit_for_rebase_autosquash_setup &&
> +	start=$(git rev-parse HEAD) &&
> +
> +	git commit --fixup=amend:HEAD -C HEAD &&
> +	git commit --fixup=amend:HEAD -C HEAD &&
> +	git log -1 --pretty=%B >with-c &&
> +
> +	git reset --hard "$start" &&
> +	test_set_editor : &&
> +	git commit --fixup=amend:HEAD &&
> +	git commit --fixup=amend:HEAD &&
> +	git log -1 --pretty=%B >without-c &&
> +
> +	test_cmp with-c without-c
> +'
> +
> +test_expect_success 'commit --fixup=amend: with -C copies full subject + body of squash commit' '
> +	commit_for_rebase_autosquash_setup &&
> +	git commit --squash HEAD~ -m "inner body" &&
> +	echo "extra" >>foo &&
> +	git add foo &&
> +	git commit --fixup=amend:HEAD -C HEAD &&
> +	test_commit_message HEAD <<-EOF
> +	amend! squash! $(git log -1 --format=%s HEAD~3)
> +
> +	squash! $(git log -1 --format=%s HEAD~3)
> +
> +	inner body
> +	EOF
> +'
> +
>   test_expect_success 'commit --fixup=reword: works with -F' '
>   	commit_for_rebase_autosquash_setup &&
>   	echo "message from file" >msgfile &&
> @@ -553,9 +609,7 @@ test_expect_success 'invalid message options when using --fixup' '
>   	echo changes >>foo &&
>   	echo "message" >log &&
>   	git add foo &&
> -	test_must_fail git commit --fixup HEAD~1 --squash HEAD~2 &&
> -	test_must_fail git commit --fixup HEAD~1 -C HEAD~2 &&
> -	test_must_fail git commit --fixup HEAD~1 -c HEAD~2
> +	test_must_fail git commit --fixup HEAD~1 --squash HEAD~2
>   '
>   
>   cat >expected-template <<EOF