revsfromrange: reuse information from the stablesort We collaborate with the stablesort to store the order that led to a merge. That way, when we needs to retrieve revision from that merge we can reuse that order. We might need to filter to only retains ancestors of the merge we care about but skipping the stablesort safe a large amount of time.

stablesort: allow a callback to be triggered on merge Storing some information as we sort is going to be useful to avoid performing multiple sort while computing the stablerange.

minor simplification around rangelength