[PATCH v2 3/3] branch: rename orphan branches in any worktree

["Rubén Justo" <rjusto@gmail.com>]

In cfaff3aac (branch -m: allow renaming a yet-unborn branch, 2020-12-13)
we added support for renaming an orphan branch, skipping rename_ref() if
the branch to rename is an orphan branch, checking the current HEAD.

But the orphan branch to be renamed can be an orphan branch in a
different working tree than the current one, i.e. not the current HEAD.

Let's make "ishead_reject_rebase_or_bisect_branch()" return a flag
indicating if the returned value refers to an orphan branch, and use it
to extend what we did in cfaff3aac, to all HEADs in the repository.

Signed-off-by: Rubén Justo <rjusto@gmail.com>
---
 builtin/branch.c  |  5 ++---
 t/t3200-branch.sh | 16 ++++++++++++++++
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index 6bb5f50950..7e6baa291a 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -495,7 +495,7 @@ static int ishead_and_reject_rebase_or_bisect_branch(const char *target)
 		struct worktree *wt = worktrees[i];
 
 		if (wt->head_ref && !strcmp(target, wt->head_ref))
-			ret = 1;
+			ret = 1 + (is_null_oid(&wt->head_oid) ? 1 : 0);
 
 		if (!wt->is_detached)
 			continue;
@@ -560,8 +560,7 @@ static void copy_or_rename_branch(const char *oldname, const char *newname, int
 		strbuf_addf(&logmsg, "Branch: renamed %s to %s",
 			    oldref.buf, newref.buf);
 
-	if (!copy &&
-	    (!head || strcmp(oldname, head) || !is_null_oid(&head_oid)) &&
+	if (!copy && !(ishead > 1) &&
 	    rename_ref(oldref.buf, newref.buf, logmsg.buf))
 		die(_("Branch rename failed"));
 	if (copy && copy_existing_ref(oldref.buf, newref.buf, logmsg.buf))
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 5a169b68d6..966583dc7d 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -279,6 +279,22 @@ test_expect_success 'git branch -M and -C fail on detached HEAD' '
 	test_cmp expect err
 '
 
+test_expect_success 'git branch -m should work with orphan branches' '
+	test_when_finished git checkout - &&
+	test_when_finished git worktree remove -f wt &&
+	git worktree add wt --detach &&
+
+	# rename orphan in another worktreee
+	git -C wt checkout --orphan orphan-foo-wt &&
+	git branch -m orphan-foo-wt orphan-bar-wt &&
+	test orphan-bar-wt=$(git -C orphan-worktree branch --show-current) &&
+
+	# rename orphan in the current worktree
+	git checkout --orphan orphan-foo &&
+	git branch -m orphan-foo orphan-bar &&
+	test orphan-bar=$(git branch --show-current)
+'
+
 test_expect_success 'git branch -d on orphan HEAD (merged)' '
 	test_when_finished git checkout main &&
 	git checkout --orphan orphan &&
-- 
2.39.0