branch -m: update all per-worktree HEADs

When renaming a branch, currently only the HEAD of current working tree
is updated, but it must update HEADs of all working trees which point at
the old branch.

This is the current behavior, /path/to/wt's HEAD is not updated:

  % git worktree list
  /path/to     2c3c5f2 [master]
  /path/to/wt  2c3c5f2 [oldname]
  % git branch -m master master2
  % git worktree list
  /path/to     2c3c5f2 [master2]
  /path/to/wt  2c3c5f2 [oldname]
  % git branch -m oldname newname
  % git worktree list
  /path/to     2c3c5f2 [master2]
  /path/to/wt  0000000 [oldname]

This patch fixes this issue by updating all relevant worktree HEADs
when renaming a branch.

Signed-off-by: Kazuki Yamaguchi <k@rhe.jp>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/branch.c b/branch.c
index c50ea42..4162443 100644
--- a/branch.c
+++ b/branch.c
@@ -344,3 +344,26 @@ void die_if_checked_out(const char *branch)
 		die(_("'%s' is already checked out at '%s'"), branch, existing);
 	}
 }
+
+int replace_each_worktree_head_symref(const char *oldref, const char *newref)
+{
+	int ret = 0;
+	struct worktree **worktrees = get_worktrees();
+	int i;
+
+	for (i = 0; worktrees[i]; i++) {
+		if (worktrees[i]->is_detached)
+			continue;
+		if (strcmp(oldref, worktrees[i]->head_ref))
+			continue;
+
+		if (set_worktree_head_symref(worktrees[i]->git_dir, newref)) {
+			ret = -1;
+			error(_("HEAD of working tree %s is not updated"),
+			      worktrees[i]->path);
+		}
+	}
+
+	free_worktrees(worktrees);
+	return ret;
+}