[GSoC PATCH v2 3/4] repo: add path.gitdir with absolute and relative suffix formatting

[K Jayatheerth <jayatheerthkulkarni2005@gmail.com>]

Scripts often need to locate the `.git` directory. While `git rev-parse`
provides this, it relies on command-line flags to dictate path formatting.

Introduce `path.gitdir.absolute` and `path.gitdir.relative` keys to
`git repo info`. Exposing separate format-specific keys instead of a base
`path.gitdir` key avoids default fallbacks and requires callers to state
their format requirements explicitly. Both keys use `format_path()` to
resolve paths.

To test these keys, introduce the `test_repo_info_path` helper in
`t/t1900-repo-info.sh`. The helper evaluates paths dynamically and accepts
environment variable prefixes. This prepares the test suite for future path
keys that depend on environment overrides, such as `commondir`.

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 |  6 ++++++
 builtin/repo.c              | 26 ++++++++++++++++++++++++++
 t/t1900-repo-info.sh        | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+)

diff --git a/Documentation/git-repo.adoc b/Documentation/git-repo.adoc
index 42262c1983..a0dca7ce88 100644
--- a/Documentation/git-repo.adoc
+++ b/Documentation/git-repo.adoc
@@ -104,6 +104,12 @@ values that they return:
 `object.format`::
 	The object format (hash algorithm) used in the repository.
 
+`path.gitdir.absolute`::
+	The canonical absolute path to the Git repository directory (the `.git` directory).
+
+`path.gitdir.relative`::
+	The path to the Git repository directory relative to the current working directory.
+
 `references.format`::
 	The reference storage format. The valid values are:
 +
diff --git a/builtin/repo.c b/builtin/repo.c
index 71a5c1c29c..6e97f6a0e4 100644
--- a/builtin/repo.c
+++ b/builtin/repo.c
@@ -7,12 +7,14 @@
 #include "hex.h"
 #include "odb.h"
 #include "parse-options.h"
+#include "path.h"
 #include "path-walk.h"
 #include "progress.h"
 #include "quote.h"
 #include "ref-filter.h"
 #include "refs.h"
 #include "revision.h"
+#include "setup.h"
 #include "strbuf.h"
 #include "string-list.h"
 #include "shallow.h"
@@ -75,6 +77,28 @@ static int get_object_format(struct repository *repo, struct strbuf *buf)
 	return 0;
 }
 
+static int get_path_gitdir_absolute(struct repository *repo, struct strbuf *buf)
+{
+	const char *git_dir = repo_get_git_dir(repo);
+
+	if (!git_dir)
+		return error(_("unable to get git directory"));
+
+	format_path(buf, git_dir, startup_info->prefix, PATH_FORMAT_CANONICAL);
+	return 0;
+}
+
+static int get_path_gitdir_relative(struct repository *repo, struct strbuf *buf)
+{
+	const char *git_dir = repo_get_git_dir(repo);
+
+	if (!git_dir)
+		return error(_("unable to get git directory"));
+
+	format_path(buf, git_dir, startup_info->prefix, PATH_FORMAT_RELATIVE);
+	return 0;
+}
+
 static int get_references_format(struct repository *repo, struct strbuf *buf)
 {
 	strbuf_addstr(buf,
@@ -87,6 +111,8 @@ 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.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 39bb77dda0..0660b00bbc 100755
--- a/t/t1900-repo-info.sh
+++ b/t/t1900-repo-info.sh
@@ -155,4 +155,37 @@ test_expect_success 'git repo info -h shows only repo info usage' '
 	test_grep ! "git repo structure" actual
 '
 
+test_repo_info_path () {
+	field_name=$1
+	expect_absolute_eval=$2
+	expect_relative=$3
+	env_prefix=$4
+
+	test_expect_success "query individual key: path.$field_name.absolute${env_prefix:+ ($env_prefix)}" '
+		(
+			cd test-repo/sub &&
+			expect_absolute=$(eval "$expect_absolute_eval") &&
+			echo "path.$field_name.absolute=$expect_absolute" >expect &&
+			eval "${env_prefix:+$env_prefix }git repo info \"path.$field_name.absolute\"" >actual &&
+			test_cmp expect actual
+		)
+	'
+
+	test_expect_success "query individual key: path.$field_name.relative${env_prefix:+ ($env_prefix)}" '
+		(
+			cd test-repo/sub &&
+			echo "path.$field_name.relative=$expect_relative" >expect &&
+			eval "${env_prefix:+$env_prefix }git repo info \"path.$field_name.relative\"" >actual &&
+			test_cmp expect actual
+		)
+	'
+}
+
+test_expect_success 'setup test repository layout for path fields' '
+	git init test-repo &&
+	mkdir -p test-repo/sub
+'
+
+test_repo_info_path 'gitdir' 'echo "$(cd .. && pwd)/.git"' '../.git'
+
 test_done
-- 
2.54.0