set_worktree_head_symref(): fix error message

Emit an informative error when failed to hold lock of HEAD.

2233066e (refs: add a new function set_worktree_head_symref,
2016-03-27) added set_worktree_head_symref(), but this is missing a
call to unable_to_lock_message() after hold_lock_file_for_update()
fails, so it emits an empty error message:

  % git branch -m oldname newname
  error:
  error: HEAD of working tree /path/to/wt is not updated
  fatal: Branch renamed to newname, but HEAD is not updated!

Thanks to Eric Sunshine for pointing this out.

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

0 files changed, 0 insertions, 0 deletions