convert: make filemap renames consistently override revision renames When the source repository had a revision renaming "$new -> $old", but the filemap a "$old -> $new" rename, the converted revision could use either $new (deleting the file) or $old (keeping the file) when getting the file data, depending on the lexicographical order of those names. So the resulting revision would leave some files untouched (as expected), but delete others arbitrarely.

obsolete: compute extinct changesets `extinct` changesets are obsolete changesets with obsolete descendants only. They are of no interest anymore and can be: - exclude from exchange - hidden to the user in most situation - safely garbage collected This changeset just allows mercurial to detect them. The implementation is a bit naive, as for unstable changesets. We better use a simple revset query and a cache, but simple version comes first.