docs: def clone_from(repo_url, repo_dir):
      """Clone a remote git repo into a local directory."""
      repo_url = _fix_repo_url(repo_url)
      LOG.info("Cloning %s into %s." % (repo_url, repo_dir))
      cmd = GIT_CLONE_CMD.format(repo_url, repo_dir)
      resp = envoy.run(cmd)
      if resp.status_code != 0:
          LOG.error("Cloned failed: %s" % resp.std_err)
          raise GitException(resp.std_err)
      LOG.info("Clone successful.")