Git supports the concept of alternate object databases. Compared to other products, Gerrit currently does not offer users to fork a repository.
The use cases for forks could be manifold: From personal workspaces to eventually supporting pull requests. More generally: A place where one can use all of the upstream data, yet, doesn't pollute the upstream repo with unfinished work.
In this lightning talk I'll go over some CUJs and talk about technical background.