Add a new file consisting of given blob IDs.

def AddFileWithUnknownHash(client_path, blob_refs, use_external_stores=True):
  """Add a new file consisting of given blob IDs."""
  precondition.AssertType(client_path, db.ClientPath)
  precondition.AssertIterableType(blob_refs, rdf_objects.BlobReference)
  return AddFilesWithUnknownHashes(
      {client_path: blob_refs},
      use_external_stores=use_external_stores)[client_path]