title: how to reference a YAML "setting" from elsewhere in the same YAML file?
body: <p>I have the following YAML:</p>
  
  <pre><code>paths:
    patha: /path/to/root/a
    pathb: /path/to/root/b
    pathc: /path/to/root/c
  </code></pre>
  
  <p>How can I "normalise" this, by removing <code>/path/to/root/</code> from the three paths, and have it as its own setting, something like:</p>
  
  <pre><code>paths:
    root: /path/to/root/
    patha: *root* + a
    pathb: *root* + b
    pathc: *root* + c
  </code></pre>
  
  <p>Obviously that's invalid, I just made it up. What's the real syntax? Can it be done?</p>