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, 7 insertions, 0 deletions

diff --git a/branch.h b/branch.h
index 78ad438..d69163d 100644
--- a/branch.h
+++ b/branch.h
@@ -60,4 +60,11 @@ extern int read_branch_desc(struct strbuf *, const char *branch_name);
  */
 extern void die_if_checked_out(const char *branch);
 
+/*
+ * Update all per-worktree HEADs pointing at the old ref to point the new ref.
+ * This will be used when renaming a branch. Returns 0 if successful, non-zero
+ * otherwise.
+ */
+extern int replace_each_worktree_head_symref(const char *oldref, const char *newref);
+
 #endif