Add revset function corresponding to git sw commits

[pokey]

Would be nice to have a revset function that returns the same set of commits that appear in the git switch quick pick. Was planning to use this for POC VSCode extension

Alternately, is there a simple way to express this set of commits using today's revset functionality?

[arxanas]

I think the commits are just draft()?

[pokey]

Didn't seem exactly the same. It also includes the head of main I believe. And for some reason it seemed to include a couple fewer commits, but I couldn't figure out which it was missing, as I wasn't sure how to dump the output to a file for diffing 🤔

[arxanas]

@pokey oh, you probably want the set of commits described here: #492