The best way to move your git repo onto Nostr, and escape the clutches of GitHub, is to just lock your repo on GitHub to Issues and Proposals/PRs. I'm serious. Just go cold-turkey and write:
"please submit issues and proposals to: https://gitworkshop.dev/r/naddrbunchofnumbers"
You can still use it as a gitserver, but maybe go ahead and try to set up a new gitserver, or use https://codeberg.org or something.
As long as you have your GitHub repo open for interaction, that is where the interaction will be because people are creatures of habit. GitHub has a strong network effect that makes everyone mindless GitHub drones.
GitHub Zombies