treemanifest: fix debugrebuildfncache When I taught debugrebuildfncache about dirlogs in fb92927f9775 (treemanifests: fix streaming clone, 2016-02-04), I added a last-minute "if 'treemanifest' in repo" guard. That should have been checking for "... in repo.requirements". Fix that and add tests for it.

update: warn about other topological head in pull and unbundle Other commands have a '--update' triggering a bare update. We now issue the message introduced into the previous changeset for these too.