test failure when renames produce similar similarities
test illustrating tri-cyclic rename failure
Fix rename looped reference issues

This makes the diff rename tracking code more careful about the
order in which it processes renames and more thorough in updating
the mapping of correct renames when an earlier rename update
alters the index of a later matched pair.
Merge pull request #1659 from arrbee/rename-cycle-fixes

Diff rename detection cycle fixes