The differ for branch+edits wasn't correctly including the original filename or

revision in the diff. The result of this was that files which were copied only

would show up properly, though the "Copied from ..." line would be wrong. Files

that were copied and then edited would fail to patch, since the original

version wasn't correctly found.
This change fixes it up so we set the oldFilename and oldVersion correctly

for both renames and copies.

Posted a change that involved a branch+edit of a file. Before this change, I

saw a patch failure in the diff viewer. After, I see the diff I expect.