Expose KnownGraph off of VersionedFiles handle ghosts (needs tests, doesn't seem to effect performance) list(tuple[1:]) is a couple ms slower than using my own loop. Net effect is: time bzr log -n0 -r -10..-1 real 0m2.559s
time wbzr log -n0 -r -10..-1 real 0m1.170s
time bzr log -n1 -r -10..-1 real 0m0.453s
So the overhead for the extra graph is down from 2.1s to 0.7s