To colaborate on a gist:
- Clone your gist repo locally
- Add your friend’s fork as a remote
e.g. if your friend is named Cindy:
git remote add-url cindy https://gist.github.com/cindy/df03bdacaef75a80f310
- Fetch your friend’s commits:
git fetch cindy/master
- Merge your friend’s changes into your repo:
git merge cindy/master
- Push the changes back to GitHub:
git push origin/master
That is something else than collaboration?