code: func (cs Set) ProjectAndRef() (project, ref string) {
  	domain, project, ref := cs.Split()
  	if domain == "projects" {
  		return
  	}
  	return "", ""
  }
docs: // ProjectAndRef splits a project-rooted config set (projects/<name>[/...]) into
  // its project name and ref components.
  //
  // For example, "projects/foo/bar/baz" is a config set that belongs to project
  // "foo". It will be parsed into ("foo", "bar/baz").
  //
  // If configSet is not a project config set, empty strings will be returned.