more tests:
- Run all tests against repository with revprop changing allowed and without
- performance tests (count roundtrips?)
- upgrades from v3
- bzr svn-set-revprops

performance:
- generate deltas rather than fulltexts when creating file id maps for the cache
- fix copyfrom in replay and replay_range
- faster function for finding all *existing* branches
- automatically disable cache in some situations, allow partial cache?
 - perhaps for large repositories?
- special LRU cache for revisionmetadata

for other things to do, see:

* https://bugs.launchpad.net/bzr-svn
