Paperclip Duplicate Checker

Author	Tim Morgan
Version	1.0 (Apr 20, 2012)
License	Released under the MIT license.

This class extends Paperclip, adding a feature that forgoes uploading a replacement for an existing attachment file if the replacement is identical to the existing file.

In order for this to work, your model _must_have an <attachment>_fingerprint column, since MD5 fingerprints are used for comparison. To use, simply follow this example:

class MyModel < ActiveRecord::Base
  include CheckForDuplicateAttachedFile
  has_attachment :note
  check_for_duplicate_attached_file :note
end

Et voila! You save on bandwidth costs if your code re-uploads a lot of the same files.