branch: do not rename a branch under bisect or rebase

The branch name in that case could be saved in rebase's head_name or
bisect's BISECT_START files. Ideally we should try to update them as
well. But it's trickier (*). Let's play safe and see if the user
complains about inconveniences before doing that.

(*) If we do it, bisect and rebase need to provide an API to rename
branches. We can't do it in worktree.c or builtin/branch.c because
when other people change rebase/bisect code, they may not be aware of
this code and accidentally break it (e.g. rename the branch file, or
refer to the branch in new files). It's a lot more work.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/branch.c

@@ -524,6 +524,29 @@ static void print_ref_list(struct ref_filter *filter, struct ref_sorting *sortin
 	ref_array_clear(&array);
 }
 
+static void reject_rebase_or_bisect_branch(const char *target)
+{
+	struct worktree **worktrees = get_worktrees();
+	int i;
+
+	for (i = 0; worktrees[i]; i++) {
+		struct worktree *wt = worktrees[i];
+
+		if (!wt->is_detached)
+			continue;
+
+		if (is_worktree_being_rebased(wt, target))
+			die(_("Branch %s is being rebased at %s"),
+			    target, wt->path);
+
+		if (is_worktree_being_bisected(wt, target))
+			die(_("Branch %s is being bisected at %s"),
+			    target, wt->path);
+	}
+
+	free_worktrees(worktrees);
+}
+
 static void rename_branch(const char *oldname, const char *newname, int force)
 {
 	struct strbuf oldref = STRBUF_INIT, newref = STRBUF_INIT, logmsg = STRBUF_INIT;
@@ -553,6 +576,8 @@ static void rename_branch(const char *oldname, const char *newname, int force)
 
 	validate_new_branchname(newname, &newref, force, clobber_head_ok);
 
+	reject_rebase_or_bisect_branch(oldref.buf);
+
 	strbuf_addf(&logmsg, "Branch: renamed %s to %s",
 		 oldref.buf, newref.buf);
 

t/t2025-worktree-add.sh

@@ -254,6 +254,10 @@ test_expect_success 'not allow to delete a branch under rebase' '
 	)
 '
 
+test_expect_success 'rename a branch under rebase not allowed' '
+	test_must_fail git branch -M under-rebase rebase-with-new-name
+'
+
 test_expect_success 'check out from current worktree branch ok' '
 	(
 		cd under-rebase &&
@@ -276,4 +280,8 @@ test_expect_success 'checkout a branch under bisect' '
 	)
 '
 
+test_expect_success 'rename a branch under bisect not allowed' '
+	test_must_fail git branch -M under-bisect bisect-with-new-name
+'
+
 test_done

worktree.c

@@ -216,8 +216,8 @@ const char *get_worktree_git_dir(const struct worktree *wt)
 		return git_common_path("worktrees/%s", wt->id);
 }
 
-static int is_worktree_being_rebased(const struct worktree *wt,
-				     const char *target)
+int is_worktree_being_rebased(const struct worktree *wt,
+			      const char *target)
 {
 	struct wt_status_state state;
 	int found_rebase;
@@ -234,8 +234,8 @@ static int is_worktree_being_rebased(const struct worktree *wt,
 	return found_rebase;
 }
 
-static int is_worktree_being_bisected(const struct worktree *wt,
-				      const char *target)
+int is_worktree_being_bisected(const struct worktree *wt,
+			       const char *target)
 {
 	struct wt_status_state state;
 	int found_rebase;

worktree.h

@@ -42,6 +42,9 @@ extern void free_worktrees(struct worktree **);
 extern const struct worktree *find_shared_symref(const char *symref,
 						 const char *target);
 
+int is_worktree_being_rebased(const struct worktree *wt, const char *target);
+int is_worktree_being_bisected(const struct worktree *wt, const char *target);
+
 /*
  * Similar to git_path() but can produce paths for a specified
  * worktree instead of current one