branch: abort if closing branch from a non-branchhead cset
This patch make sure that we abort if the user is trying to
close a branch from a cset which is not a branch head.
Changes in test file reflect the fixed behaviour.
Differential Revision: https://phab.mercurial-scm.org/D6282
# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)