setdiscovery: use revsets for computing a subset's heads and roots
revlogdag.headsetofconnecteds() obtains the set of DAG heads in a
given set of revs.
revlogdag.inverse() inverts the DAG order and makes
headsetofconnecteds() obtain the DAG roots in a given subset.
Both of these can be expressed with a revset.
Like other patches in this series, revlogdag uses revlog.index
and thus doesn't take filtering into account. Revsets do. So there
is a chance for regressions with this change. But no tests fail.
And I think this code should take filtering into account since
hidden changesets shouldn't factor into discovery (unless operating
on the hidden repository).
Differential Revision: https://phab.mercurial-scm.org/D4321
# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)