Can't you just run gitlab or whatever else out of a container in 5 seconds nowadays? Map a single volume and you are likely done. Its not that it's hard to self host that I choose to use third party git services (its clearly not!), it's just that the benefits of self hosting a git repository are increasingly few unless you have strict security requirements etc etc, and the free options are so good now. Running self hosted git is trivial in 2022 if you really need to, with many one-line container deployment options to choose from.
> https://registry.hub.docker.com/r/gitlab/gitlab-ce/
While it might be fun to self-host, a 5 dollar a month fee to run it is also not price competitive with the free or paid individual tiers at github.com for a single user too. I'd probably only do this if the git repo was being hosted on my home LAN.