Yeah, Hg's repository format (at least the last time I saw it) is actually a CVS-like individual-file thing, with the atomic commits and stuff layered on top of that. I think all hg rename does is leave a note on the new file that it was copied from the old deleted file. (But it's been a while since I actually cared, and it's late enough at night that I probably shouldn't be trusted with the Internet right now.)