I'm not entirely sure what you mean, but it's worth mentioning that you can have more than one remote for a git repo. You can pull and push from whichever remotes you want.
How can you do that ?
Well, "origin", though default, is just a name. Name of a "Remote repo" wherever that is ;)
Git is great because it's f simple!
You can have multiple remotes, and the situation will be like github forks, only may differ from it in permissions.
I think auth and permissions are not git's direct responsibility, though I many be wrong about it.
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