checkheahds: switch algorithm to use pushed markers instead We now checks if markers involved in the push are relevant to nodes in the branch we try to replace. The approach is simpler and more robust. A test showing the limitation of the previous approach is added.

checkheads: add test where the rewrite of the other branch is not direct This will help testing that our logic is properly transitive.

check-heads: add tests about old heads indirectly pruned

checkheads: add more complexe case where a branch is split on multiple ones We extend case A-6 and A-7 with partial counterpart. These case are interesting because some of the partial pushing will (rightfully) works and some other won't.

checkheads: add a test of partially pushing a branch spread on multiple other If a branch is fully obsolete but is result are spread on multiple branch, pushing only one of them should detect we create new branches.

checkheads-tests: add missing parents recording for prune markers It is a bit too easy to forget about theses :/ If they are missing, the markers are not going to be exchanged on push.