title: One mapping to toggle NERDTree and open to current file when toggling on
body: <p>I'm trying to find a way to have a normal mode mapping that can toggle NERDTree, but when toggling on, tell NERDTree to find the current file.</p>
  
  <p>I know about <code>NERDTreeToggle</code> and <code>NERDTreeFind</code>, and what I'm looking to do is essentially a combination of those two commands.</p>
  
  <p>Here's my use case:</p>
  
  <ol>
  <li>When NERDTree is not open, I can hit <code>&lt;C-\&gt;</code> and NERDTree will open to the current file.</li>
  <li>I can then hit <code>&lt;C-\&gt;</code> again and NERDTree will close.</li>
  </ol>