branchmap: encapsulate cache updating in the map itself
Rather than have a repository update the cache, move handling of cache updates
into the branchmap module, in the form of a custom mapping class.
This makes later performance improvements easier to handle too.
Differential Revision: https://phab.mercurial-scm.org/D5638
# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)