It seems that fetch() no longer returns the number of revisions fetched. It still does for *some* InterRepository fetch paths, but the generic one does not. It is also not easy to get it to, since the Source and Sink are the ones that would know how many keys were transmitted, and they are potentially 'remote' objects.
This was also only tested to occur as a by-product in a random 'test_commit' test. I assume if we really wanted the assurance, we would have a per_repo or interrepo test for it.