title: Superfluous warnings when using maven-shade-plugin
body: <p>I am using <em>maven-shade-plugin</em> for a simple maven project, the plugin successfully includes all the dependencies into a final "shaded" jar. The process works well every time and produces exactly what I need.</p>
  
  <p>When run the "first" time (after a <code>clean</code>), the plugin is quiet and produces very little output. However, when re-run (without a <code>clean</code> from the last build), there are lots of warning messages such as this; </p>
  
  <pre><code>[WARNING] We have a duplicate package/a/b/foo.class
  [WARNING] We have a duplicate package/c/d/bar.class
  </code></pre>
  
  <p>This are warning messages only and the final artifact works fine. </p>
  
  <p>My question is simple: how can I safely workaround or suppress these warning messages without having to run a <code>clean</code> first? </p>
  
  <hr>
  
  <p><em>note:</em> A possible solution would be to move to the <em>maven-assembly-plugin</em>, but I would prefer not to because the configuration for <em>maven-shade-plugin</em> is very nice and simple. </p>