infer current pull request or pipeline from repository

For commands that need to know the pr or pipeline gcli should be acting on, when these are omitted, gcli should try and infer which one the user meant. E.g. when on a feature branch, the pr should be the pr created from that feature branch (if that is unambiguous) and the pipeline should be the latest that ran for the thus found pr, or if there's no pr, the latest that ran for the branch.

(This idea comes from how glab behaves).