title: The diff command for files with empty content
body: <p>If I want to get the difference between the 2 directories, I use the command below:</p>
  
  <pre><code>diff -aruN dir1/ dir2/ &gt; dir.patch
  </code></pre>
  
  <p>so the dir.patch file should comprise all differences I want, right?</p>
  
  <p>But if <code>dir2/</code> contains a file with empty content, and that file is not existent in <code>dir1/</code>, for example,</p>
  
  <pre><code>dir1/
  
  dir2/empty_content_file.txt ------ with empty content.
  </code></pre>
  
  <p>Then the diff command will not generate any patch for empty_content_file.txt, but it is a needed file.</p>
  
  <p>Is there any expertise or alternative way to do this?</p>
  
  <p>Thank you in advance.</p>