title: Generating Shake Rules from Actions
body: <p>I would like find all of the 'Makefiles' in my project and then generate
  Rules based them.
  However, it looks like (purposely) nothing can escape an Action.
  So, Instead I lifted my 'Makefile' scanner to the IO operation before the
  shake function.</p>
  
  <pre><code>main = do
    makefiles &lt;- findMakefiles
    shake skakeOptions $ generate_rules makefiles
  </code></pre>
  
  <p>Is there a better way?</p>