def _TailSet(start_point, listing):
  """Returns set of object name tails.

  Tails can be compared between source and dest, past the point at which rsync
  was done.  For example if test ran rsync gs://bucket1/dir gs://bucket2/dir2,
  the tails for listings from bucket1 would start after "dir", while the tails
  for listings from bucket2 would start after "dir2".

  Args:
    start_point: The target of the rsync command, e.g., for the above command it
                 would be gs://bucket1/dir for the bucket1 listing results and
                 gs://bucket2/dir2 for the bucket2 listing results.
    listing: The listing over which to compute tail.

  Returns:
    Object name tails.
  """
  return set(l[len(start_point):] for l in listing.strip().split('\n'))