code: def git(self, username, repo, alias=None, token=None):
          
          if alias is None:
              alias = repo
          if token is None:
              token = os.environ.get('GITHUB_TOKEN')
          self.wait('mkdir -p %s' % alias)
          old_dir = self.pwd
          try:
              self.chdir(alias, relative=True)
              cmd = 'git init && git pull https://%s@github.com/%s/%s.git'
              # last line to stderr
              return self.wait(cmd % (token, username, repo),
                               raise_on_error=False)
          finally:
              self.chdir(old_dir, relative=False)
docs: Parameters
          ----------
          token: str, default None
              Assumes you have GITHUB_TOKEN in envvar if None
  
          https://github.com/blog/1270-easier-builds-and-deployments-using-git-
          over-https-and-oauth