stash: fix incorrect branch name in stash message

When creating a stash, Git uses the current branch name
of the superproject to construct the stash commit message.
However, in repositories with submodules,
the message may mistakenly display the submodule branch name instead.

This is because `refs_resolve_ref_unsafe()` returns a pointer to a static buffer.
Subsequent calls to the same function overwrite the buffer,
corrupting the originally fetched `branch_name` used for the stash message.

Use `xstrdup()` to duplicate the branch name immediately after resolving it,
so that later buffer overwrites do not affect the stash message.

Signed-off-by: K Jayatheerth <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: jayatheerthkulkarni

builtin/stash.c

@@ -1373,6 +1373,7 @@ static int do_create_stash(const struct pathspec *ps, struct strbuf *stash_msg_b
 	const char *head_short_sha1 = NULL;
 	const char *branch_ref = NULL;
 	const char *branch_name = "(no branch)";
+	char *branch_name_buf = NULL;
 	struct commit *head_commit = NULL;
 	struct commit_list *parents = NULL;
 	struct strbuf msg = STRBUF_INIT;
@@ -1405,8 +1406,12 @@ static int do_create_stash(const struct pathspec *ps, struct strbuf *stash_msg_b
 
 	branch_ref = refs_resolve_ref_unsafe(get_main_ref_store(the_repository),
 					     "HEAD", 0, NULL, &flags);
-	if (flags & REF_ISSYMREF)
-		skip_prefix(branch_ref, "refs/heads/", &branch_name);
+
+	if (flags & REF_ISSYMREF) {
+		if (skip_prefix(branch_ref, "refs/heads/", &branch_name))
+			branch_name = branch_name_buf = xstrdup(branch_name);
+	}
+
 	head_short_sha1 = repo_find_unique_abbrev(the_repository,
 						  &head_commit->object.oid,
 						  DEFAULT_ABBREV);
@@ -1496,6 +1501,7 @@ static int do_create_stash(const struct pathspec *ps, struct strbuf *stash_msg_b
 	strbuf_release(&msg);
 	strbuf_release(&untracked_files);
 	free_commit_list(parents);
+	free(branch_name_buf);
 	return ret;
 }
 

t/t3903-stash.sh

@@ -1592,4 +1592,36 @@ test_expect_success 'stash apply reports a locked index' '
 	)
 '
 
+test_expect_success 'submodules does not affect the branch recorded in stash message' '
+	git init sub_project &&
+	(
+		cd sub_project &&
+		echo "Initial content in sub_project" >sub_file.txt &&
+		git add sub_file.txt &&
+		git commit -m "Initial commit in sub_project"
+	) &&
+
+	git init main_project &&
+	(
+		cd main_project &&
+		echo "Initial content in main_project" >main_file.txt &&
+		git add main_file.txt &&
+		git commit -m "Initial commit in main_project" &&
+
+		git -c protocol.file.allow=always submodule add ../sub_project sub &&
+		git commit -m "Added submodule sub_project" &&
+
+		git checkout -b feature_main &&
+		git -C sub checkout -b feature_sub &&
+
+		git checkout -b work_branch &&
+		echo "Important work to be stashed" >work_item.txt &&
+		git add work_item.txt &&
+		git stash push -m "custom stash for work_branch" &&
+
+		git stash list >../actual_stash_list.txt &&
+		grep "On work_branch: custom stash for work_branch" ../actual_stash_list.txt
+	)
+'
+
 test_done