revert: don't assume ignored files will be returned in the unknown list
That's just an artifact of the current implementation, and I'll change
that soon.
Bonus points:
- we don't care about the unknown list at all
- we don't print an extra message if we try to revert a removed file
that is not present in the target revision
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
removing b
abort: update spans branches, use 'hg merge' or 'hg update -C' to lose changes