Suggestion: rebase [--onto <newbase>] [<upstream>][..[<branch>]]

I think
	git rebase [--onto <newbase>] [<upstream>][..[<branch>]]
would be a more readable syntax for what rebase is doing.  Easier
to see which argument means what without staring at the manpage.
"..[<branch>]" without <upstream> implies --root.

-- 
Hallvard