title: Ack — Ignoring multiple directories without repeating the flag
body: <p>Is it possible to ignore multiple directories in Ack, without repeating the flag?</p>
  
  <p>e.g. I know the following <em>works</em> (i.e. setting multiple flags):</p>
  
  <pre><code>ack --ignore-dir=install --ignore-dir=php 'teststring'
  </code></pre>
  
  <p>I was hoping that I could separate directories with commas, like I can do with the extensions as follows:</p>
  
  <pre><code>ack --ignore-file=ext:css,scss,orig 'teststring'
  </code></pre>
  
  <p>However, the following comma separated ignore flag doesn't work:</p>
  
  <pre><code>ack --ignore-dir=install,php 'textstring'
  </code></pre>
  
  <p>Is it possible to use some short-hand equivalent, so I don't have to repeatedly type out the --ignore-dir flag?</p>