Git rename ref replacing "X" with "X/Y"

When pulling tags from git, handle the situation where a Git ref gets turned into a directory:

  File "/usr/local/lib/python3.10/dist-packages/breezy/branch.py", line 1074, in pull
    return InterBranch.get(source, self).pull(
  File "/usr/local/lib/python3.10/dist-packages/breezy/git/branch.py", line 1323, in pull
    with self.target.lock_write(), self.source.lock_read():
  File "/usr/local/lib/python3.10/dist-packages/breezy/git/branch.py", line 558, in lock_write
    self._lock_ref()
  File "/usr/local/lib/python3.10/dist-packages/breezy/git/branch.py", line 784, in _lock_ref
    self._ref_lock = self.repository._git.refs.lock_ref(self.ref)
  File "/usr/local/lib/python3.10/dist-packages/breezy/git/transportgit.py", line 374, in lock_ref
    gf = GitFile(local_path, 'wb')
  File "/usr/local/lib/python3.10/dist-packages/dulwich/file.py", line 92, in GitFile
    return _GitFile(filename, mode, bufsize, mask)
  File "/usr/local/lib/python3.10/dist-packages/dulwich/file.py", line 150, in __init__
    fd = os.open(
NotADirectoryError: [Errno 20] Not a directory: '/tmp/janitorsitau7aw/ecbuild.git/.git/refs/heads/upstream/latest.lock'

See https://janitor.debian.net/cupboard/pkg/poppler-data/02a764dc-8939-4ac4-bf18-fed1fb15425a/