title: Copy multiple directories with one command
body: <p>Is there any way to copy multiple directories in one command, to reduce the number of layers? E.g., instead of:</p>
  
  <pre><code>COPY dirone ./dirone
  COPY dirtwo ./dirtwo
  COPY dirthree ./dirthree
  </code></pre>
  
  <p>I want to do:</p>
  
  <pre><code>COPY dirone/ dirtwo/ dirthree/ ./
  </code></pre>
  
  <p>However, this copies the <em>contents</em> of the directories... but I want to copy <em>the directories themselves</em>.</p>