"git rebase -i" did not clear the state files correctly when a run
of "squash/fixup" is aborted and then the user manually amended the
commit instead, which has been corrected.

* js/rebase-i-autosquash-fix:
  rebase -i: be careful to wrap up fixup/squash chains
  rebase -i --autosquash: demonstrate a problem skipping the last squash