revset: add partial support for ancestor(wdir()) It's easy, so let's make it happen. I'm not certain if 'wdir() &' should be required. ancestors(wdir()) works without it, but ancestor(wdir()) doesn't as of now. That's the issue of fullreposet.__contains__() vs __and__().

context: also accept diff option directly For now we accept both diff option and dictionary. This will let us upgrade internal users gradually before we drop the old API at the end of this series.