rebase: abort if the user tries to rebase the working copy I think it's more correct to treat `hg rebase -r 'wdir()' -d foo` as `hg co -m foo`, but I'm instead making it error out. That's partly because it's probably what the user wanted (in the case I heard from a user, they had done `hg rebase -s f` where `f` resolved to `wdir()`) and partly because I don't want to think about more complicated cases where the user specifies the working copy together with other commits. Differential Revision: https://phab.mercurial-scm.org/D8057