BuildGitHostname builds the hostname of a cluster-local git repo from the provided namespace.

CreateKnownHosts works around https://github.com/go-git/go-git/issues/411.

GetExternalRepoAddr retrieves the external URL where our local git server can be reached, based on the provided port and repo name.

NewHTTP creates a new Git instance with HTTP auth, using environment variables.

NewSSH creates a new Git instance with SSH auth, using environment variables.

Git represents a git repo with auth.