If self-hosted, somewhere, you could still be screwed by having Dyn as your DNS provider.
If dev-machine-hosted, then uh, your issue tracker is no longer an issue tracker. Your build server is not a build server. All the services besides Git are not meant to operate offline in a decentralized/distributed fashion.
Library documentation, sure, that could be local. Otherwise, your assertion that all of this tools infrastructure can somehow be replicated, easily, in a way that makes the difference between working online or offline effectively zero, is nonsense.