topic: reorder revset for faster evaluation When running the revset on unfiltered repository, the mutable set can get huge. So removing the obsolete changeset first provide a large speedup. This resolve the performance regression we were seeing since the 6.7.0 release.

# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)