[Martin]
> Looking at the code, I find it unfortunate that it uses os.path.exists,
> causing a stat call, and then does another stat call to find the time stamp.

Are you noting the inefficiency of doing two stat calls instead of one, or saying that it should make none at all in dry-run mode?  My opinion is that a dry-run mode should not create any file nor make any changes, but reading files and calling processes that give info is fair game.