title: mv: "Directory not Empty" - how do you merge directories with `mv`?
body: <p>I tried to deploy my personal blog website to my remote server recently. When I tried to move a few files and directories to another place by executing <code>mv</code>, some unexpected errors happened. The command line echoed &quot;Directory not Empty&quot;. After doing some googling, I tried again with '<strong>-f</strong>' switch or '<strong>-v</strong>', the same result showed.
  I logged in on the <strong>root</strong> account, and the process is here:</p>
  <pre><code>root@danielpan:~# shopt -s dotglob
  root@danielpan:~# mv /var/www/html/wordpress/* /var/www/html
  mv: cannot move `/var/www/html/wordpress/wp-content` to `/var/www/html/wp-content`: 
  Directory not empty
  root@danielpan:~# mv -f /var/www/html/wordpress/* /var/www/html
  mv: cannot move `/var/www/html/wordpress/wp-content` to `/var/www/html/wp-content`:
  Directory not empty
  </code></pre>
  <p>Anybody know why?</p>
  <p>(I'm running Ubuntu 14.04)</p>