title: Updating Paperclip path file names from on server to s3
body: <p>I have a paperclip instance that I am migrating my files to a different area. Originally the files were stored on my server and just given a filename based on the id of the record created and the original id. Now I'm moving them to s3 and want to update the filenames to work appropriately. I setup my paperclip config like so:</p>
  
  <pre><code>:path =&gt; ":class/:attachment/:hash-:style.:extension",
      :url =&gt; ":s3_domain_url",
      :hash_secret =&gt; SECRET,
      :hash_data =&gt; ":class/:attachment/:id/:updated_at"
  </code></pre>
  
  <p>I updated the original records filenames for my files to be unique and moved them over to my s3 instance. Unfortunately now I am unable to pull down the files from s3 and I think it is because paperclip is using the wrong path for the filenames. One that is based off the path default that is now set using my config file. I want to be able to update my files file_name field so that the path is correct for the new files and I am able to download them appropriately. Is there a way to call paperclips hashing function based on my secret and hash_data directly so I can update those file_name fields and be able to pull those records now? Everything that has been uploaded since the move from my original servers seems to work appropriately.</p>