Git is decentralized as is. It stores all the history locally and sends a copy to GitHub AND/OR any other repo you would like. GitHub is just a part of decentralized git ecosystem. It simplifies communication. But I agree - it is good to use more than one repository. And in case of Bitcoin code it is crucial to use several different private repos owned by different people.
So, what I understand, as Git is already decentralized, we just need to increase hubs to decentralize Github. Right?
Git is distributed more so as it allows you to distribute the copy to other developers who each store their own copy and each works on their own copy still it is not decentralized. Each developer is pulling from the manager a central authority.
You can read more here.
https://git-scm.com/book/en/v1/Distributed-Git-Distributed-WorkflowsStill the reason it is not decentralized is because the copy that developers are pulling from is not distributed in a trust-less manner. Instead of having to go through the manager only for the pull, one should be allowed to go through any trust-less party in who holds a valid copy while at the same time when a update is made all trust-less party holding a copy must update theirs to be current & valid also. You can as stated put them up in different repos but this still would not be full decentralization it would be more of a federated system as it is limited.
I just read this blog
https://medium.com/@alexberegszaszi/mango-git-completely-decentralised-7aef8bcbcfe6and it shows that projects are actually working on making git fully decentralized.
Stating that there are projects such as Mango which runs on Ethereum, GitTorrent which runs on Bitcoin and Git-SSB.
Would be neat to keep tabs on such projects, maybe there isn't enough popularity because they do not have to do with Cryptocurrency instead solely the use of Blockchain for the better of the people. We as a community need to promote the use of these projects and stand together. It isn't all about money in this space.