title: Appending rather than overwriting files when moving
body: <p>I have the following directory structure:</p>
  
  <pre><code>+-archive
    +-a
      +-data.txt
    +-b
      +-data.txt 
  +-incoming
    +-a
      +-data.txt
    +-c
      +-data.txt
  </code></pre>
  
  <p>How do I do the equivalent of <code>mv incoming/* archive/</code> but have the contents of the files in <code>incoming</code> appended to those in <code>archive</code> rather than overwrite them?</p>