Merge branch 'jc/remove-treesame-parent-in-simplify-merges'

The --simplify-merges logic did not cull irrelevant parents from a merge that is otherwise not interesting with respect to the paths we are following. This touches a fairly core part of the revision traversal infrastructure; even though I think this change is correct, please report immediately if you find any unintended side effect. * jc/remove-treesame-parent-in-simplify-merges: simplify-merges: drop merge from irrelevant side branch