You mean a “github repo”. Git by itself doesn’t give a hoot about validating authors what-so-ever (I could sign as “Bill Gates bill@microsoft.com”, and git would happily accept the commit), and it’s not federated (multiple people manually downloading various states of the repo at various times doesn’t count).

Github ensures owners are who they are, as linked to their profile (though email validation only goes as far as “Well, they clicked the link in the email, so this must be their email account”). Github also isn’t federated, since that one site going down takes all the repos with it (unless someone had it cloned, but again, random people downloading at random times yields different states of the repo, depending on when the clone/fetch occured, but then you’d end up with tens/hundreds/thousands of sources of various levels of truth).