title: How to make Vim plugin NERDTree's <CR> behave more like `go`?
body: <p>In NERDTree, <code>&lt;CR&gt;</code> is same as shortcut <code>o</code> which in its help doc is described as below:</p>
  
  <pre><code>Default key: o
  Map option: NERDTreeMapActivateNode
  Applies to: files and directories.
  
  If a file node is selected, it is opened in the previous window.
  
  If a directory is selected it is opened or closed depending on its current
  state.
  
  If a bookmark that links to a directory is selected then that directory
  becomes the new root.
  
  If a bookmark that links to a file is selected then that file is opened in the
  previous window.
  </code></pre>
  
  <p>I want to <strong>open a file with the cursor just remained in the NERDTree</strong>. </p>
  
  <p>I found it's just the action that shortcut <code>go</code> does. But <code>go</code> can only be applied to <code>files</code> while <code>o</code> is applied to <code>files and directories</code>.</p>
  
  <p>In the NERDTree's help doc:</p>
  
  <pre><code>Default key: go
  Map option: None
  Applies to: files.
  
  If a file node is selected, it is opened in the previous window, but the
  cursor does not move.
  
  The key combo for this mapping is always "g" + NERDTreeMapActivateNode (see
  NERDTree-o).
  </code></pre>
  
  <p>More specifically, I want <code>&lt;CR&gt;</code> to behave as <code>o</code> when applied to <code>directories</code>, and <code>go</code> when <code>files</code>.</p>
  
  <p>There is no <code>Customisation</code> flag to do that.</p>
  
  <p>Is there any good way to implement it including modifying the source script?  </p>
  
  <p>Thanks a lot!</p>