[PATCH v3 6/7] repo: add path.grafts with absolute and relative suffix formatting

External toolchains managing specialized history rewrites or legacy
history splices require access to the location of the repository grafts
file. Currently, this requires a legacy call to `git rev-parse --git-path info/grafts`.

Introduce `path.grafts.absolute` and `path.grafts.relative` keys to
`git repo info`. This allows scripting layers to query the active grafts
context cleanly while scaling transparently with active `GIT_GRAFT_FILE`
environment variable overrides.

Mentored-by: Justin Tobler <[email protected]>
Mentored-by: Lucas Seiki Oshiro <[email protected]>
Signed-off-by: K Jayatheerth <[email protected]>
---
 Documentation/git-repo.adoc | 10 ++++++++++
 builtin/repo.c              | 24 ++++++++++++++++++++++++
 t/t1900-repo-info.sh        |  6 ++++++
 3 files changed, 40 insertions(+)

diff --git a/Documentation/git-repo.adoc b/Documentation/git-repo.adoc
index 34c4f7d61c..def888da91 100644
--- a/Documentation/git-repo.adoc
+++ b/Documentation/git-repo.adoc
@@ -119,6 +119,16 @@ values that they return:
 `path.gitdir.relative`::
 	The path to the Git repository directory relative to the current working directory.
 
+`path.grafts.absolute`::
+	The canonical absolute path to the repository grafts file.
+	Respects the `GIT_GRAFT_FILE` environment override. The path is returned
+	regardless of whether the file currently exists on disk.
+
+`path.grafts.relative`::
+	The path to the repository grafts file relative to the current working
+	directory. Respects the `GIT_GRAFT_FILE` environment override. The path
+	is returned regardless of whether the file currently exists on disk.
+
 `path.hooks.absolute`::
 	The canonical absolute path to the repository's hooks directory.
 	Respects `core.hooksPath` configuration adjustments.
diff --git a/builtin/repo.c b/builtin/repo.c
index 66bf4c67cc..a97ad71649 100644
--- a/builtin/repo.c
+++ b/builtin/repo.c
@@ -122,6 +122,28 @@ static int get_path_gitdir_relative(struct repository *repo, struct strbuf *buf)
 	return 0;
 }
 
+static int get_path_grafts_absolute(struct repository *repo, struct strbuf *buf)
+{
+	const char *graft_file = repo_get_graft_file(repo);
+
+	if (!graft_file)
+		return error(_("unable to get graft file"));
+
+	format_path(buf, graft_file, startup_info->prefix, PATH_FORMAT_CANONICAL);
+	return 0;
+}
+
+static int get_path_grafts_relative(struct repository *repo, struct strbuf *buf)
+{
+	const char *graft_file = repo_get_graft_file(repo);
+
+	if (!graft_file)
+		return error(_("unable to get graft file"));
+
+	format_path(buf, graft_file, startup_info->prefix, PATH_FORMAT_RELATIVE);
+	return 0;
+}
+
 static int get_path_hooks_absolute(struct repository *repo, struct strbuf *buf)
 {
 	struct strbuf hooks_path = STRBUF_INIT;
@@ -258,6 +280,8 @@ static const struct repo_info_field repo_info_field[] = {
 	{ "path.commondir.relative", get_path_commondir_relative },
 	{ "path.gitdir.absolute", get_path_gitdir_absolute },
 	{ "path.gitdir.relative", get_path_gitdir_relative },
+	{ "path.grafts.absolute", get_path_grafts_absolute },
+	{ "path.grafts.relative", get_path_grafts_relative },
 	{ "path.hooks.absolute", get_path_hooks_absolute },
 	{ "path.hooks.relative", get_path_hooks_relative },
 	{ "path.index.absolute", get_path_index_absolute },
diff --git a/t/t1900-repo-info.sh b/t/t1900-repo-info.sh
index dee1db2a49..15a4ec9b78 100755
--- a/t/t1900-repo-info.sh
+++ b/t/t1900-repo-info.sh
@@ -213,6 +213,12 @@ test_repo_info_path 'gitdir with explicit GIT_DIR' 'gitdir' \
 	'.git' \
 	'GIT_DIR="../.git" && export GIT_DIR'
 
+test_repo_info_path 'grafts standard' 'grafts' '.git/info/grafts'
+
+test_repo_info_path 'grafts with GIT_GRAFT_FILE override' 'grafts' \
+	'custom-graft-file' \
+	'GIT_GRAFT_FILE="$ROOT/custom-graft-file" && export GIT_GRAFT_FILE'
+
 test_repo_info_path 'hooks standard fallback' 'hooks' '.git/hooks'
 
 test_repo_info_path 'hooks with core.hooksPath override' 'hooks' \
-- 
2.55.GIT