title: Preventing Paperclip from deleting/overwriting attachments on update
body: <p>I'm having a hard time figuring out how to prevent Paperclip from deleting the old version of an attachment (image).</p>
  
  <p>I have a model, Site, which has an attachment, logo. I would like to keep the old logos around since I will be keeping track of changes to the model and would like to view the history of logos.</p>
  
  <p>I'm keeping track of the changes in another model, which has a reference to file paths. My problem is that when updating a site with a new logo, Paperclip will flush the old logo first.</p>
  
  <p>It surprises me that there's not an option you can switch to prevent Paperclip from flushing the old attachment before creating the new one.</p>
  
  <p>Any ideas?</p>