title: oh-my-zsh: ignore untracked files
body: <p>Are there any options/flags/settings for <code>oh-my-zsh</code> that would make it ignore untracked files by default when setting the prompt?</p>
  
  <p>Many of my repos contain untracked files, this causes the prompt to have the little asterisk after the branch name even when there are no modified files:</p>
  
  <pre><code>matt@khea /tmp/dotfiles [master *]
  </code></pre>