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

[K Jayatheerth <jayatheerthkulkarni2005@gmail.com>]

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 <jltobler@gmail.com>
Mentored-by: Lucas Seiki Oshiro <lucasseikioshiro@gmail.com>
Signed-off-by: K Jayatheerth <jayatheerthkulkarni2005@gmail.com>
---
 Documentation/git-repo.adoc |  8 ++++++++
 builtin/repo.c              | 24 ++++++++++++++++++++++++
 t/t1900-repo-info.sh        |  6 ++++++
 3 files changed, 38 insertions(+)

diff --git a/Documentation/git-repo.adoc b/Documentation/git-repo.adoc
index 3a837c573e..6c962620ec 100644
--- a/Documentation/git-repo.adoc
+++ b/Documentation/git-repo.adoc
@@ -119,6 +119,14 @@ 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.
+
+`path.grafts.relative`::
+	The path to the repository grafts file relative to the current working
+	directory. Respects the `GIT_GRAFT_FILE` environment override.
+
 `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 04e6b8553c..6c47989df7 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