changegroup: introduce safeversion() In a few places (at least repair.py and shelve.py), we want to find the best changegroup version that we can assume users of the repo will understand. For example, we choose version 01 by default, but if it's a generaldelta repo, we expect clients to support version 02 anyway, so we choose that for new bundles (for e.g. "hg strip"). Let's create a helper for this functionality in changegroup, so we can reuse it elsewhere later.

changegroup: don't support versions 01 and 02 with treemanifests Since it would be terribly expensive to convert between flat manifests and treemanifests, we have decided to simply not support changegroup version 01 and 02 with treemanifests. Therefore, let's stop announcing that we support these versions on treemanifest repos. Note that this means that older clients that try to clone from a treemanifest repo will fail. What happens is that the server, after this patch, finds that there are no common versions and raises "ValueError: no common changegroup version". This results in "abort: HTTP Error 500: Internal Server Error" on the client. Before this patch, it was no better: The server would instead find that there were directory manifest nodes to put in the changegroup 01 or 02 and raise an AssertionError on changegroup.py#668 (assert not tmfnodes), which would also appear as a 500 to the client.