topicidx: stop assigning index number to obsolete changesets Obsolete changeset are no longer part of the stack, the old logic tried to assigns them the index of their successors but this is flacky and error prone. So we stop doing so.

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