[GSoC Patch v7 2/8] submodule: use repository to find superproject

[K Jayatheerth <jayatheerthkulkarni2005@gmail.com>]

`get_superproject_working_tree()` currently uses `xgetcwd()` to
determine the repository whose superproject should be checked.

This is incorrect when `--git-dir` points to a repository different
from the one associated with the current working directory. In that
case, the current working directory may cause the function to return
the wrong superproject or an empty result.

Pass the `repository` to `get_superproject_working_tree()` so that the
superproject is determined from the repository being inspected rather
than the current working directory.

Mentored-by: Justin Tobler <jltobler@gmail.com>
Mentored-by: Lucas Seiki Oshiro <lucasseikioshiro@gmail.com>
Signed-off-by: K Jayatheerth <jayatheerthkulkarni2005@gmail.com>
---
 builtin/rev-parse.c        |  2 +-
 submodule.c                | 43 +++++++++++++++++++-------------------
 submodule.h                |  2 +-
 t/t7400-submodule-basic.sh | 19 +++++++++++++++++
 4 files changed, 43 insertions(+), 23 deletions(-)

diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index 43693454d5..e1a6da0076 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -997,7 +997,7 @@ int cmd_rev_parse(int argc,
 			}
 			if (!strcmp(arg, "--show-superproject-working-tree")) {
 				struct strbuf superproject = STRBUF_INIT;
-				if (get_superproject_working_tree(&superproject))
+				if (get_superproject_working_tree(the_repository, &superproject))
 					print_path(superproject.buf, prefix, format, DEFAULT_UNMODIFIED);
 				strbuf_release(&superproject);
 				continue;
diff --git a/submodule.c b/submodule.c
index 6fcb606f7e..4db90ef9b0 100644
--- a/submodule.c
+++ b/submodule.c
@@ -2610,34 +2610,35 @@ void absorb_git_dir_into_superproject(const char *path,
 	absorb_git_dir_into_superproject_recurse(path, super_prefix);
 }
 
-int get_superproject_working_tree(struct strbuf *buf)
+int get_superproject_working_tree(struct repository *r, struct strbuf *buf)
 {
 	struct child_process cp = CHILD_PROCESS_INIT;
 	struct strbuf sb = STRBUF_INIT;
 	struct strbuf one_up = STRBUF_INIT;
-	char *cwd = xgetcwd();
+	struct strbuf target_wt = STRBUF_INIT;
+	const char *worktree;
 	int ret = 0;
 	const char *subpath;
 	int code;
 	ssize_t len;
 
-	if (!is_inside_work_tree(the_repository))
-		/*
-		 * FIXME:
-		 * We might have a superproject, but it is harder
-		 * to determine.
-		 */
+	worktree = repo_get_work_tree(r);
+	if (!worktree)
+		goto out;
+
+	if (!strbuf_realpath(&target_wt, worktree, 0))
 		goto out;
 
-	if (!strbuf_realpath(&one_up, "../", 0))
+	strbuf_addf(&one_up, "%s/..", target_wt.buf);
+	if (!strbuf_realpath(&one_up, one_up.buf, 0))
 		goto out;
 
-	subpath = relative_path(cwd, one_up.buf, &sb);
+	subpath = relative_path(target_wt.buf, one_up.buf, &sb);
 
 	prepare_submodule_repo_env(&cp.env);
 	strvec_pop(&cp.env);
 
-	strvec_pushl(&cp.args, "--literal-pathspecs", "-C", "..",
+	strvec_pushl(&cp.args, "--literal-pathspecs", "-C", one_up.buf,
 		     "ls-files", "-z", "--stage", "--full-name", "--",
 		     subpath, NULL);
 	strbuf_reset(&sb);
@@ -2648,14 +2649,14 @@ int get_superproject_working_tree(struct strbuf *buf)
 	cp.git_cmd = 1;
 
 	if (start_command(&cp))
-		die(_("could not start ls-files in .."));
+		die(_("could not start ls-files in %s"), one_up.buf);
 
 	len = strbuf_read(&sb, cp.out, PATH_MAX);
 	close(cp.out);
 
 	if (starts_with(sb.buf, "160000")) {
 		int super_sub_len;
-		int cwd_len = strlen(cwd);
+		int wt_len = target_wt.len;
 		char *super_sub, *super_wt;
 
 		/*
@@ -2666,12 +2667,12 @@ int get_superproject_working_tree(struct strbuf *buf)
 		super_sub = strchr(sb.buf, '\t') + 1;
 		super_sub_len = strlen(super_sub);
 
-		if (super_sub_len > cwd_len ||
-		    strcmp(&cwd[cwd_len - super_sub_len], super_sub))
-			BUG("returned path string doesn't match cwd?");
+		if (super_sub_len > wt_len ||
+		    strcmp(&target_wt.buf[wt_len - super_sub_len], super_sub))
+			BUG("returned path string doesn't match worktree?");
 
-		super_wt = xstrdup(cwd);
-		super_wt[cwd_len - super_sub_len] = '\0';
+		super_wt = xstrdup(target_wt.buf);
+		super_wt[wt_len - super_sub_len] = '\0';
 
 		strbuf_realpath(buf, super_wt, 1);
 		ret = 1;
@@ -2681,10 +2682,10 @@ int get_superproject_working_tree(struct strbuf *buf)
 	code = finish_command(&cp);
 
 	if (code == 128)
-		/* '../' is not a git repository */
+		/* parent directory is not a git repository */
 		ret = 0;
 	else if (code == 0 && len == 0)
-		/* There is an unrelated git repository at '../' */
+		/* There is an unrelated git repository at parent directory */
 		ret = 0;
 	else if (code)
 		die(_("ls-tree returned unexpected return code %d"), code);
@@ -2692,7 +2693,7 @@ int get_superproject_working_tree(struct strbuf *buf)
 out:
 	strbuf_release(&sb);
 	strbuf_release(&one_up);
-	free(cwd);
+	strbuf_release(&target_wt);
 	return ret;
 }
 
diff --git a/submodule.h b/submodule.h
index b10e16e6c0..1a465a1208 100644
--- a/submodule.h
+++ b/submodule.h
@@ -170,6 +170,6 @@ void absorb_git_dir_into_superproject(const char *path,
  * project is a submodule of. If this repository is not a submodule of
  * another repository, return 0.
  */
-int get_superproject_working_tree(struct strbuf *buf);
+int get_superproject_working_tree(struct repository *r, struct strbuf *buf);
 
 #endif
diff --git a/t/t7400-submodule-basic.sh b/t/t7400-submodule-basic.sh
index eefdecb0bd..5c3d9f2829 100755
--- a/t/t7400-submodule-basic.sh
+++ b/t/t7400-submodule-basic.sh
@@ -1549,4 +1549,23 @@ test_expect_success 'submodule add fails when name is reused' '
 	)
 '
 
+test_expect_success 'path.superproject-root works with --git-dir' '
+	test_when_finished "rm -rf sub super" &&
+	git init sub &&
+	test_commit -C sub initial &&
+	git init super &&
+	(
+		cd super &&
+		git -c protocol.file.allow=always submodule add "../sub" sub &&
+		git commit -m "add submodule" &&
+
+		SUPER_ROOT="$(test-tool path-utils real_path .)" &&
+		MODULE_DIR="$SUPER_ROOT/.git/modules/sub" &&
+
+		echo "path.superproject-root.absolute=$SUPER_ROOT" >expect &&
+		git --git-dir="$MODULE_DIR" repo info path.superproject-root.absolute >actual &&
+		test_cmp expect actual
+	)
+'
+
 test_done
-- 
2.56.0-rc2