Re: [PATCH v2] sha1-name.c: for ":/", find detached HEAD commits

> include commits reachable from HEAD but not any named ref. This avoids
> surprising behavior when working with a detached HEAD and trying to
> refer to a commit that was recently created and only exists within the
> detached state.
>
> If multiple worktrees exist, only the current worktree's HEAD is
> considered reachable. This is consistent with the existing behavior for
> other per-worktree refs: e.g., bisect refs are considered reachable, but
> only within the relevant worktree.
>
> Signed-off-by: Jeff King <peff@peff.net>
> Signed-off-by: William Chargin <wchargin@gmail.com>
> Based-on-patch-by: Jeff King <peff@peff.net>

>  Documentation/revisions.txt   |  2 +-
>  sha1-name.c                   |  1 +
>  t/t4208-log-magic-pathspec.sh | 26 ++++++++++++++++++++++++++
>  3 files changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/revisions.txt b/Documentation/revisions.txt
> index 7d1bd4409..aa9579eba 100644
> --- a/Documentation/revisions.txt
> +++ b/Documentation/revisions.txt
> @@ -184,7 +184,7 @@ existing tag object.
>    A colon, followed by a slash, followed by a text, names
>    a commit whose commit message matches the specified regular expression.
>    This name returns the youngest matching commit which is
> -  reachable from any ref. The regular expression can match any part of the
> +  reachable from any ref, including HEAD. The regular expression can match any part of the
>    commit message. To match messages starting with a string, one can use
>    e.g. ':/^foo'. The special sequence ':/!' is reserved for modifiers to what
>    is matched. ':/!-foo' performs a negative match, while ':/!!foo' matches a
> diff --git a/sha1-name.c b/sha1-name.c
> index 60d9ef3c7..641ca12f9 100644
> --- a/sha1-name.c
> +++ b/sha1-name.c
> @@ -1650,6 +1650,7 @@ static int get_oid_with_context_1(const char *name,
>  			struct commit_list *list = NULL;
>  
>  			for_each_ref(handle_one_ref, &list);
> +			head_ref(handle_one_ref, &list);
>  			commit_list_sort_by_date(&list);
>  			return get_oid_oneline(name + 2, oid, list);
>  		}
> diff --git a/t/t4208-log-magic-pathspec.sh b/t/t4208-log-magic-pathspec.sh
> index 62f335b2d..4c8f3b8e1 100755
> --- a/t/t4208-log-magic-pathspec.sh
> +++ b/t/t4208-log-magic-pathspec.sh
> @@ -25,6 +25,32 @@ test_expect_success '"git log :/a -- " should not be ambiguous' '
>  	git log :/a --
>  '
>  
> +test_expect_success '"git log :/detached -- " should find a commit only in HEAD' '
> +	test_when_finished "git checkout master" &&
> +	git checkout --detach &&
> +	# Must manually call `test_tick` instead of using `test_commit`,
> +	# because the latter additionally creates a tag, which would make
> +	# the commit reachable not only via HEAD.
> +	test_tick &&
> +	git commit --allow-empty -m detached &&
> +	test_tick &&
> +	git commit --allow-empty -m something-else &&
> +	git log :/detached --
> +'
> +
> +test_expect_success '"git log :/detached -- " should not find an orphaned commit' '
> +	test_must_fail git log :/detached --
> +'
> +
> +test_expect_success '"git log :/detached -- " should find HEAD only of own worktree' '
> +	git worktree add other-tree HEAD &&
> +	git -C other-tree checkout --detach &&
> +	test_tick &&
> +	git -C other-tree commit --allow-empty -m other-detached &&
> +	git -C other-tree log :/other-detached -- &&
> +	test_must_fail git log :/other-detached --
> +'
> +
>  test_expect_success '"git log -- :/a" should not be ambiguous' '
>  	git log -- :/a
>  '