rebase: make sure the newancestor is used during the whole update (issue1561) Before this change, newancestor was used only once as a replacement for ancestor.ancestor, but merge.update calls ancestor.ancestor several times, so it ends up with the "wrong" ancestor (the real ancestor, but we want the parent of the rebased changeset for all but the first rebased changeset). Added a new test case for this: test-rebase-newancestor. Also, in one scenario in test-rebase-collapse, there was a spurious conflict caused by the same issue, so that test case was fixed by removing the now unneeded conflict resolution and the output was adapted accordingly.