title: Set Django's FileField to an existing file
body: <p>I have an existing file on disk (say /folder/file.txt) and a FileField model field in Django.</p>
  
  <p>When I do </p>
  
  <pre><code>instance.field = File(file('/folder/file.txt'))
  instance.save()
  </code></pre>
  
  <p>it re-saves the file as <code>file_1.txt</code> (the next time it's <code>_2</code>, etc.).</p>
  
  <p>I understand why, but I don't want this behavior - I know the file I want the field to be associated with is really there waiting for me, and I just want Django to point to it.</p>
  
  <p>How?</p>