Tests for pruning GitLab branches on topic rename/retarget
This reproduces heptapod#134 (closed), adding the case of the retargetting (i.e., branch of topic changeset has changed) and a sanity check for the fix.
This reproduces heptapod#134 (closed), adding the case of the retargetting (i.e., branch of topic changeset has changed) and a sanity check for the fix.