gistfile1.txt

Actually, you don't need to do that. GitHub provides a special pulls remote "namespace" on the upstream repo, so you can add it as a fetch pattern to your .git/config like so:
    [remote "upstream"]
      url = https://github.com/neovim/neovim.git
      fetch = +refs/heads/*:refs/remotes/upstream/*
      fetch = +refs/pull/*/head:refs/pull/upstream/*
Then when you `git fetch --all`, you will have ALL pull requests available in your local repo in the local pull/ namespace. To check out PR #42:
    git checkout -b foo refs/pull/upstream/42