test-pathencode: compare current pathencoding implementations We already have two implementations of the pathencoding (C and Python) and this test can perfectly well be used to probabilistically test them instead of just wasting CPU cycles and test time.

rebase: use lazy ancestor membership testing For a repository with over 400,000 commits, rebasing one revision near tip, this avoids one walk up the DAG, speeding the operation up by around 0.8 seconds.