copies: handle more cases where a file got replaced by a copy This patch fixes the changeset-centric version in a pretty straight-forward way. It fixes it to automatically resolve the conflict, which is better than resulting in a modify/delete conflict as it was before b4057d001760 (merge: when rename was made on both sides, use ancestor as merge base, 2020-01-22). I'll leave it for later to test and explicitly handle cases where files have been renamed to the same target on different sides of the merge. Differential Revision: https://phab.mercurial-scm.org/D8653