debugobsolete: extract marker display in a dedicated function We want to be able to reuse and extend it from other function or extension while working on markers exchange. This changeset is pure core movement.

exchange: extract pull function from localrepo The localrepo class if far too big. Push and pull logic are extracted and reworked to better fit with the fact we exchange more than bundle now. This changeset extract the pulh code. later changeset will slowly slice it into smaller brick. The localrepo.pull method is kept for now to limit impact on user code. But it will be ultimately removed, now that the public API is hold by peer.

push: extract new common set computation from phase synchronisation Now that every necessary information is held in the `pushoperation` object, we can extract the new common set computation to it's own function. This changeset is pure code movement only.