If two mp3 files in the same directory have identical id3tags,
running mp3rename on both will rename them both to the same filename.
Naturally, this results in the loss of one of the files' content.

(Not filing as grave to not be an asshole and because my files are
backed up 6 ways to sunday and checked into git too, so this behavior
was only a little puzzling and not data-loss.)

I think that mp3rename should either bail out, or add something to make
a unique filename in this case.