One of the cool things with the update adding git support to GitHub Wiki was that it was using gollum (
https://github.com/gollum/gollum) and GitHub wanted to become more open source themselves (
https://github.blog/2010-08-12-making-github-more-open-git-b...). Sadly, it seems like they have diverged by now, according to the GitHub Wiki on the gollum repository.
Seems there is still some historical artifacts from it left.