title: watch with rsync fails with permission denied, while rsync alone just works fine
body: <p>I'm trying to sync my files to cloud:</p>
  
  <pre><code>rsync -avPze "ssh -i /path/to/my/key" [source] [destination]
  </code></pre>
  
  <p>this works successfully for me.</p>
  
  <p>However, when I try to use the same command with <code>watch</code> in order to sync automatically every couple minutes, it doesn't work and throws error:</p>
  
  <pre><code>watch -n120 rsync -avPze "ssh -i /path/to/my/key" [source] [destination]
  </code></pre>
  
  <p>Error:</p>
  
  <pre><code>Permission denied (publickey).
  rsync: connection unexpectedly closed (0 bytes received so far) [sender]
  rsync error: unexplained error (code 255) at io.c(226) [sender=3.1.1]
  </code></pre>
  
  <p>Any idea what is going on?</p>