StGIT unhelpfulness

  Hi,

  I tried to stg pull to my git repository at repo.or.cz, but stg pull
only laconically announced

	stg pull: Rebasing would possibly lose data

and left me with a confused stare. The same with popping all the patches first, so there is actually nothing _to_ rebase, but it still fails.

  Five minutes of peeking at the stgit code later, I think this is
because I sometimes do stg pull (now) and sometimes stg pop -a, cg
update, stg push -a when I'm feeling nostalgic. orig-base doesn't get
updated and stgit gets unhappy, but frankly, I don't even get _why_ does
it need to record and check orig-base - how does it matter?

  Besides, when it doesn't like it, it should give me some more helpful
error message than just the cryptic above...