title: How can I split horizontally across several vertically split windows in Vim?
body: <p>Basically, I want to go from <strong>1)</strong> to <strong>2)</strong>
  I usually do this by splitting horizontally first and then vertically, but as I want this to do three-way diffs, it is much handier to start vim by running:</p>
  
  <pre><code>$ vimdiff file1 file2 file3
  </code></pre>
  
  <p>And then doing something to open the split window below.</p>
  
  <pre><code>1)
      +----+----+----+
      ¦    ¦    ¦    ¦
      ¦ f1 ¦ f2 ¦ f3 ¦
      ¦    ¦    ¦    ¦
      +----+----+----+
  
  2)
      +----+----+----+
      ¦    ¦    ¦    ¦
      ¦ f1 ¦ f2 ¦ f3 ¦
      +----+----+----+
      ¦      f4      ¦
      +--------------+
  </code></pre>
  
  <p>Does anyone know of a way to this?</p>