It would be nice if you could specify the userId to be used in headless mode, so you can identify its changes in the history...

To do this, I'd:
1. Allow you to pass options to Firepad.Headless (another options hash), and let one of those options be the "userId" and pass that through to the Fire
2. Make FirebaseAdapter take an options hash instead of individual userId and userColor.
3. Add a "headless" option, and check that here instead of userId.
4. Have Firepad.Headless pass { headless: true } to FirebaseAdapter or { headless: true, userId: blah } if Firepad.Headless was provided a userId in its options.

You don't have to do this, but it'd be nice. :-)