Comment 3 for bug 120542

We could store device/inode for the files along with the other stat info, and catch attempted dupes that way. Of course, that also wouldn't let us version more than one link to the same file, and Murphy dictates somebody will want to...

Does add another couple hunks of info to the struct that we'd only need for this one case, though. Maybe it's cheap enough to generate and check on the fly for case-differing-only files at 'add' time?