title: app.yaml skip_files skip an entire directory but one individual file
body: <p>I have an <code>app.yaml</code> file in which I want to skip the entire <code>node_modules</code> directory save for one file I added called <code>helpers.js</code>. Currently my file looks like this:</p>
  
  <pre><code>runtime: nodejs
  vm: true
  skip_files:
   - ^node_modules$
  </code></pre>
  
  <p>What's the best way of skipping the entire <code>node_modules</code> directory <strong>except</strong> for <code>helpers.js</code>?</p>