How the “GitHub” system is implemented in websites such as Hugging Face, Vercel etc

The question is pretty much it. I want to figure out how I can implement Github system into a web application. By Github system I mean the repository, branches, commits, version controls etc. Looking at the Hugging face, for example, you can see that pretty much all of the components of sharing models, datasets are implemented via GitHub. So far I was able to find APIs for Github but I highly doubt that all of this components are using APIs.

Thank you in advance!