e->sha, should return
    list of shas to fetch. Defaults to all shas.
  progress: Optional progress function
  depth: Depth to fetch at
  ref_prefix: List of prefixes of desired references, as a list of
    bytestrings. Filtering is done by the server if supported, and
    client side otherwise.
  filter_spec: A git-rev-list-style object filter spec, as bytestring.
    Only used if the server supports the Git protocol-v2 'filter'
    feature, and ignored otherwise.
  protocol_version: Desired Git protocol version. By default the highest
    mutually supported protocol version will be used.

Returns:
  Dictionary with all remote refs (not just those fetched)

Nr