alt Hacker NewsThere isn't much advantage that can be taken from O/S users and perms anyway, at least as far as git is concerned. When using a shared-filesystem repository over SSH (or NFS etc.), the actually usable access levels are: full, including the abilities to rewrite history, forge commits from other users, and corrupt/erase the repo; read-only; and none.
Git was build to be decentralized with everyone having its own copy. If it's an organization someone trusted will hold the key to the canonical version. If you need to discuss and review patches, you use a communication medium (email, forums, IRC, shared folder,...)