refs: update worktree HEADs when renaming branches

Whenever we rename a branch, we update the repository's symbolic HEAD
reference if it currently points to the branch that is to be renamed.
But with the introduction of worktrees, we also have to iterate over all
HEADs of linked worktrees to adjust them. Do so.

src/refs.c

@@ -614,19 +614,52 @@ int git_reference_symbolic_set_target(
 		out, ref->db->repo, ref->name, target, 1, ref->target.symbolic, log_message);
 }
 
+typedef struct {
+    const char *old_name;
+    git_refname_t new_name;
+} rename_cb_data;
+
+static int update_wt_heads(git_repository *repo, const char *path, void *payload)
+{
+	rename_cb_data *data = (rename_cb_data *) payload;
+	git_reference *head;
+	char *gitdir = NULL;
+	int error = 0;
+
+	if (git_reference__read_head(&head, repo, path) < 0 ||
+	    git_reference_type(head) != GIT_REF_SYMBOLIC ||
+	    git__strcmp(head->target.symbolic, data->old_name) != 0 ||
+	    (gitdir = git_path_dirname(path)) == NULL)
+		goto out;
+
+	/* Update HEAD it was pointing to the reference being renamed */
+	if ((error = git_repository_create_head(gitdir, data->new_name)) < 0) {
+		giterr_set(GITERR_REFERENCE, "failed to update HEAD after renaming reference");
+		goto out;
+	}
+
+out:
+	git_reference_free(head);
+	git__free(gitdir);
+
+	return error;
+}
+
 static int reference__rename(git_reference **out, git_reference *ref, const char *new_name, int force,
 				 const git_signature *signature, const char *message)
 {
+	git_repository *repo;
 	git_refname_t normalized;
 	bool should_head_be_updated = false;
 	int error = 0;
 
 	assert(ref && new_name && signature);
 
-	if ((error = reference_normalize_for_repo(
-		normalized, git_reference_owner(ref), new_name, true)) < 0)
-		return error;
+	repo = git_reference_owner(ref);
 
+	if ((error = reference_normalize_for_repo(
+		normalized, repo, new_name, true)) < 0)
+		return error;
 
 	/* Check if we have to update HEAD. */
 	if ((error = git_branch_is_head(ref)) < 0)
@@ -637,14 +670,18 @@ static int reference__rename(git_reference **out, git_reference *ref, const char
 	if ((error = git_refdb_rename(out, ref->db, ref->name, normalized, force, signature, message)) < 0)
 		return error;
 
-	/* Update HEAD it was pointing to the reference being renamed */
-	if (should_head_be_updated &&
-		(error = git_repository_set_head(ref->db->repo, normalized)) < 0) {
-		giterr_set(GITERR_REFERENCE, "failed to update HEAD after renaming reference");
-		return error;
+	/* Update HEAD if it was pointing to the reference being renamed */
+	if (should_head_be_updated) {
+		error = git_repository_set_head(ref->db->repo, normalized);
+	} else {
+		rename_cb_data payload;
+		payload.old_name = ref->name;
+		memcpy(&payload.new_name, &normalized, sizeof(normalized));
+
+		error = git_repository_foreach_head(repo, update_wt_heads, &payload);
 	}
 
-	return 0;
+	return error;
 }
 
 

tests/worktree/refs.c

@@ -131,6 +131,20 @@ void test_worktree_refs__delete_succeeds_after_pruning_worktree(void)
 	git_reference_free(branch);
 }
 
+void test_worktree_refs__renaming_reference_updates_worktree_heads(void)
+{
+	git_reference *head, *branch, *renamed;
+
+	cl_git_pass(git_branch_lookup(&branch, fixture.repo,
+		    "testrepo-worktree", GIT_BRANCH_LOCAL));
+	cl_git_pass(git_reference_rename(&renamed, branch, "refs/heads/renamed", 0, NULL));
+	cl_git_pass(git_repository_head(&head, fixture.worktree));
+
+	git_reference_free(head);
+	git_reference_free(branch);
+	git_reference_free(renamed);
+}
+
 void test_worktree_refs__creating_refs_uses_commondir(void)
 {
 	   git_reference *head, *branch, *lookup;

tests/worktree/worktree.c

@@ -486,3 +486,46 @@ void test_worktree_worktree__prune_both(void)
 
 	git_worktree_free(wt);
 }
+
+static int read_head_ref(git_repository *repo, const char *path, void *payload)
+{
+	git_vector *refs = (git_vector *) payload;
+	git_reference *head;
+
+	GIT_UNUSED(repo);
+
+	cl_git_pass(git_reference__read_head(&head, repo, path));
+
+	git_vector_insert(refs, head);
+
+	return 0;
+}
+
+void test_worktree_worktree__foreach_head_gives_same_results_in_wt_and_repo(void)
+{
+	git_vector repo_refs = GIT_VECTOR_INIT, worktree_refs = GIT_VECTOR_INIT;
+	git_reference *heads[2];
+	size_t i;
+
+	cl_git_pass(git_reference_lookup(&heads[0], fixture.repo, GIT_HEAD_FILE));
+	cl_git_pass(git_reference_lookup(&heads[1], fixture.worktree, GIT_HEAD_FILE));
+
+	cl_git_pass(git_repository_foreach_head(fixture.repo, read_head_ref, &repo_refs));
+	cl_git_pass(git_repository_foreach_head(fixture.worktree, read_head_ref, &worktree_refs));
+
+	cl_assert_equal_i(repo_refs.length, ARRAY_SIZE(heads));
+	cl_assert_equal_i(worktree_refs.length, ARRAY_SIZE(heads));
+
+	for (i = 0; i < ARRAY_SIZE(heads); i++) {
+		cl_assert_equal_s(heads[i]->name, ((git_reference *) repo_refs.contents[i])->name);
+		cl_assert_equal_s(heads[i]->name, ((git_reference *) repo_refs.contents[i])->name);
+		cl_assert_equal_s(heads[i]->name, ((git_reference *) worktree_refs.contents[i])->name);
+
+		git_reference_free(heads[i]);
+		git_reference_free(repo_refs.contents[i]);
+		git_reference_free(worktree_refs.contents[i]);
+	}
+
+	git_vector_free(&repo_refs);
+	git_vector_free(&worktree_refs);
+}