[GSoC][PATCH 4/4] repo: add path.commondir with absolute and relative suffix formatting

[K Jayatheerth <jayatheerthkulkarni2005@gmail.com>]

Introduce `path.commondir.absolute` and `path.commondir.relative` keys
to `git repo info`. These track the repository's common directory path,
extending the path metadata engine alongside the existing `gitdir` fields.

Update `repo_info_field` to store the new keys in proper lexicographical
order to protect binary search operations, and expand the test matrix in
`t/t1900-repo-info.sh` to validate separate queries, bulk dumps, and
key listings.

Signed-off-by: K Jayatheerth <jayatheerthkulkarni2005@gmail.com>
Mentored-by: Justin Tobler <jltobler@gmail.com>
Mentored-by: Lucas Seiki Oshiro <lucasseikioshiro@gmail.com>
---
 Documentation/git-repo.adoc |  9 +++++++++
 builtin/repo.c              | 24 ++++++++++++++++++++++++
 t/t1900-repo-info.sh        |  1 +
 3 files changed, 34 insertions(+)

diff --git a/Documentation/git-repo.adoc b/Documentation/git-repo.adoc
index a0dca7ce88..ed7d80c690 100644
--- a/Documentation/git-repo.adoc
+++ b/Documentation/git-repo.adoc
@@ -104,6 +104,15 @@ values that they return:
 `object.format`::
 	The object format (hash algorithm) used in the repository.
 
+`path.commondir.absolute`::
+	The canonical absolute path to the Git repository's common
+	directory (the shared `.git` directory containing objects,
+	refs, and global configuration).
+
+`path.commondir.relative`::
+	The path to the Git repository's common directory relative to
+	the current working directory.
+
 `path.gitdir.absolute`::
 	The canonical absolute path to the Git repository directory (the `.git` directory).
 
diff --git a/builtin/repo.c b/builtin/repo.c
index c141ef892a..be24a5a8e8 100644
--- a/builtin/repo.c
+++ b/builtin/repo.c
@@ -77,6 +77,28 @@ static int get_object_format(struct repository *repo, struct strbuf *buf)
 	return 0;
 }
 
+static int get_path_commondir_absolute(struct repository *repo, struct strbuf *buf)
+{
+	const char *common_dir = repo_get_common_dir(repo);
+
+	if (!common_dir)
+		return error(_("unable to get common directory"));
+
+	strbuf_add_path(buf, common_dir, startup_info->prefix, PATH_FORMAT_CANONICAL, PATH_DEFAULT_UNMODIFIED);
+	return 0;
+}
+
+static int get_path_commondir_relative(struct repository *repo, struct strbuf *buf)
+{
+	const char *common_dir = repo_get_common_dir(repo);
+
+	if (!common_dir)
+		return error(_("unable to get common directory"));
+
+	strbuf_add_path(buf, common_dir, startup_info->prefix, PATH_FORMAT_RELATIVE, PATH_DEFAULT_UNMODIFIED);
+	return 0;
+}
+
 static int get_path_gitdir_absolute(struct repository *repo, struct strbuf *buf)
 {
 	const char *git_dir = repo_get_git_dir(repo);
@@ -111,6 +133,8 @@ static const struct repo_info_field repo_info_field[] = {
 	{ "layout.bare", get_layout_bare },
 	{ "layout.shallow", get_layout_shallow },
 	{ "object.format", get_object_format },
+	{ "path.commondir.absolute", get_path_commondir_absolute },
+	{ "path.commondir.relative", get_path_commondir_relative },
 	{ "path.gitdir.absolute", get_path_gitdir_absolute },
 	{ "path.gitdir.relative", get_path_gitdir_relative },
 	{ "references.format", get_references_format },
diff --git a/t/t1900-repo-info.sh b/t/t1900-repo-info.sh
index 7c7dfbb052..dd2706e1f7 100755
--- a/t/t1900-repo-info.sh
+++ b/t/t1900-repo-info.sh
@@ -184,6 +184,7 @@ test_expect_success 'setup test repository layout for path fields' '
 	mkdir -p test-repo/sub
 '
 
+test_repo_info_path 'commondir' '../.git'
 test_repo_info_path 'gitdir' '../.git'
 
 test_done
-- 
2.54.0