title: How to trigger a Jenkins build in Gerrit Trigger on change to project subdirectory
body: <p>I want to trigger a Jenkins build with Gerrit Trigger only when a change to a file in a specific sub-directory is made. For example...</p>
  
  <pre><code>├── subdir1
  │   ├── trigger
  │   ├── also-trigger
  ├── subdir2
  │   ├── do-not-trigger
  </code></pre>
  
  <p>If any change to a file in subdir1 is made I want to trigger a build.</p>