Feature Request: Squash multiple commits into one

[richardtop]

CMD+S is a great way to squash commits. However, if I'd like to squash multiple commits into one (i.e. squash a branch because it has a lot of commits of "work in progress" quality and I'd like to have a single commit in the pull request after I've finished working), I'd have to press CMD+S multiple times until I squash evertything.

I'd suggest an interface similar to #917 and having an option to "squash selected commits" into one, e.g.: