title: Show version controlled files that would otherwise be ignored by current .gitignore
body: <p>The title says it all. </p>
  
  <p>For a simple example: at time t1, the repository contains files with extensions <code>.A</code> and <code>.B</code>. At a later time t2, we decide to add <code>.B</code> extensions to the <code>.gitignore</code> file. I'd like to list files with extension <code>.B</code> currently under version control (not to remove them, just to know if/where they are). </p>
  
  <p>Of course in my case it's not just one extension but many different patterns that have been added to the <code>.gitignore</code>. And it is also something useful to know for general maintenance purposes.</p>
  
  <p>Note: I'm not interested in ignored files not under version control, I know you can list those using <code>git status -i</code>.</p>