checkheads: use "revnum" in the "allfuturecommon" set The obsolete post-processing needs to know the extend of the pushed set. The way it is implemented is... suboptimal. It build a full set of all nodes in the pushset and it does so using changectx. We have much better API for this now. The simplest is to use the existing lazy ancestors computation. That logic uses revnum and not node (for good reason) so we start with updating the post-processing code to handle a "allfuturecommon" set containing revision numbers.