It's not as simple as it sounds. What if there's already a file called "stuff.txt (other guy's version)"? There's lots and lots of edge cases. You basically need a function that can always return an appropriate but not-already-existing filename.
It tries to copy the Dropbox conflict behaviour.
Although, if I'm reading this correctly, the logic isn't quite right. It uses the timestamp of the time when the conflict is detected, when it should really use the conflicted file's last-modified time, or maybe the timestamp of the conflicting commit.