Support "-" for latest branch in git rebase

[r-murphy]

Sanity checks

• [X] I have searched github.com/withfig/fig/issues and there are no duplicates of my feature

Feature Details

Description:

Please include a detailed description of the feature (and an image or screen recording, if applicable)

fig supports "-" for latest branch in checkout, switch, and merge, but not in rebase. It will be a nice to have for rebase as well. Without that it autocompletes an option like '--abort' after typing 'git rebase -' and hitting enter.

I'm happy to submit a PR for it.

Thanks