error when synchronizing repository outside master branch

[tony]

❯ vcspull django
fatal: ref HEAD is not a symbolic ref
Traceback (most recent call last):
  File "/Users/me/Library/Python/2.7/bin/vcspull", line 11, in <module>
    sys.exit(cli.cli())
  File "/Users/me/Library/Python/2.7/lib/python/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/Users/me/Library/Python/2.7/lib/python/site-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/Users/me/Library/Python/2.7/lib/python/site-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/Users/me/Library/Python/2.7/lib/python/site-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/Users/me/Library/Python/2.7/lib/python/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/Users/me/Library/Python/2.7/lib/python/site-packages/vcspull/cli.py", line 107, in update
    list(map(update_repo, found_repos))
  File "/Users/me/Library/Python/2.7/lib/python/site-packages/vcspull/cli.py", line 125, in update_repo
    r.update_repo()
  File "/Users/me/Library/Python/2.7/lib/python/site-packages/libvcs/git.py", line 157, in update_repo
    symref = self.run(['symbolic-ref', '--short', 'HEAD'])
  File "/Users/me/Library/Python/2.7/lib/python/site-packages/libvcs/base.py", line 105, in run
    cwd=cwd
  File "/Users/me/Library/Python/2.7/lib/python/site-packages/libvcs/util.py", line 178, in run
    raise exc.CommandError(output=output, returncode=code, cmd=cmd)
libvcs.exc.CommandError: Command failed with code 128: git symbolic-ref --short HEAD

~/study/django/django tags/2.0