code: func (h *stiGit) Checkout(repo, ref string) error {
  	opts := cmd.CommandOpts{
  		Stdout: os.Stdout,
  		Stderr: os.Stderr,
  		Dir:    repo,
  	}
  	if log.V(1) {
  		return h.RunWithOptions(opts, "git", "checkout", ref)
  	}
  	return h.RunWithOptions(opts, "git", "checkout", "--quiet", ref)
  }
docs: // Checkout checks out a specific branch reference of a given git repository