evolve: handle relocation during divergence resolution producing no changes When resolving divergence and the two divergent commits have different parents, we start by rebasing one of them to have the same parent as the other. That step can result in no changes to commit. When it does, we would crash with a TypeError before this patch. This patch fixes it by instead creating an empty commit in that scenario. The existing code then continues to attempt to merge it, which produces no changes, and no commit is created on top. The other side of the divergence is marked as successor as usual, so orphans from the side that became empty will be evolved to the right place (see test).

# Copyright 2019 Pierre-Yves David <pierre-yves.david@octobus.net>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

def hastopicext(repo):
    """True if the repo use the topic extension"""
    return getattr(repo, 'hastopicext', False)