Comment 9 for bug 483388

There is a workaround to this:

(1) Cherry pick and copy files as necessary to get the "merge" in order.
(2) Edit merge.py to force it to pick a specific LCA.
(3) Perform the merge, revert any changes (in the merge-protecting way), and commit.

Step two is possible by adding a line to merge.py:
             lcas = self.revision_graph.find_lca(revisions[0], revisions[1])
+ lcas = set([list(lcas)[0]])
             self._is_criss_cross = False

You may need to force a different revision (other than the one in index zero) depending on the merge topology.