pull: move return code in the pull operation object With bundle2 we'll have multiple code path susceptible to be responsible for adding changeset during the pull. We move it to the pull operation to simplify this the coming logic. The one doing the adding the changegroup will set the value.

merge: use ancestor filename from planning phase instead of filectx ancestor test-merge-types.t changes a bit in flag merging. It relied on the implementation detail that 100% identical revlog entries are reused. The revlog reuse did that fctx.ancestor() saw an ancestor where there really not was one.

tests: prevent test-hup from hanging forever if the transaction does not start If the transaction fails to start because of some programing errors, the test would stay stuck in this while loop forever. We now added a basic safeguard that abort the loop if nothing happen in 10 seconds. 10 seconds sounds enough to let the server catch up and open a transaction.