title: Use backend branch when starting server on frontend branch
body: <p>I don't know how to ask this question correctly. I have following case:</p>
  
  <p>There are several branches in the project </p>
  
  <ul>
  <li>master
  
  <ul>
  <li>frontend
  
  <ul>
  <li>feature branch</li>
  </ul></li>
  <li>backend</li>
  </ul></li>
  </ul>
  
  <p>Frontend and backend branches are readonly, so is master. I'm working on frontend feature branch and starting npm server there, but I need it to use backend code from backend branch to check if requests work correctly etc. How do I do that?</p>