Fix "unknown repository" of an opened PR after deleted the fork

Unfortunately it looks like your pull-request will remain an orphan.

See this (still unresolved) thread: https://github.com/isaacs/github/issues/168

Probably the best thing to do would be to re-clone the repo, re-create your pull-request, delete the existing pull-request, and submit a fresh one.

Also, add a "thumbs up" to tohe issue so in the future there can be a more straight-forward solution to this problem.

You can reclaim orphaned pull requests as

git fetch <remote> refs/pull/<pr_number>/head:<local-branch>

git checkout <local-branch>