ys correspond to the build config to run and the values
        are the command to run in that config. The typical use case here is
        <code class="code">opt</code> vs. <code class="code">dbg</code> but
        arbitrary names can be given and specified with
        <code class="code">plz build -c name</code>.
      </span>
    </li>
  </ul>

  <p>
    There are various special sequence replacements that the rule is subject to:
  </p>

  <ul class="bulleted-list">
    <li>
      <span>
        <code cl