revert: take fast path also when not reverting to '.' This speeds up 'hg revert -r .^ --all --dry-run' on the Mozilla repo from 4.081s to 0.826s. Note that 'hg revert -r .^ .' does not get any faster, since '.' does not make match.always() True. I can't think of a reason it would break anything, and if it does, it's clearly not covered by tests.