scc should have better support for use against external repos #224
Description
When managing a fork of an external repo it would be nice to use scc to merge individual upstream PRs into the fork. At present scc merge -D none fetches all PRs, and all are mentioned as excluded in the merge commit message. This is impractical, both in terms of the time taken to fetch all PRs, and the length of the merge commit message, when an external repo contains ~100+ PRs.