merge-slicing: avoid doing the same work twice We have already computed the list of revision in that bottom slice as 'hrevs' so we do not need to compute it a second time.

stablerange: fix a bug when a top slice ended on a merge Our "smart" detection of merge was buggy if the top slice ended on a merge. This is not fixed and tested.

slicesrangeat: stop double setting the revsinranges cache The cache should have already been filled by the logic warming the cache for the parent.