title: ignore lines with particular words in vimdiff output
body: <p>I have 2 large files to take vimdiff. In vimdiff output I want to ignore lines showing diff but  have a particular word.</p>
  
  <p>e.g. in my case I want to ignore diff of all lines with prefix <code>WARNING:</code>  in my files. </p>
  
  <p>Thanks, </p>