Added partition_id as an interpolation

git-svn-id: https://svn.thoughtbot.com/plugins/paperclip/trunk@402 7bbfaf0e-4d1d-0410-9690-a8bb5f8ef2aa

lib/paperclip/attachment.rb

@@ -127,6 +127,9 @@ module Paperclip
           File.extname(attachment.original_filename).gsub(/^\.+/, "")
           File.extname(attachment.original_filename).gsub(/^\.+/, "")
         end,
         end,
         :id           => lambda{|attachment,style| attachment.instance.id },
         :id           => lambda{|attachment,style| attachment.instance.id },
+        :partition_id => lambda do |attachment, style|
+          ("%09d" % attachment.instance.id).scan(/\d{3}/).join("/")))
+        end
         :attachment   => lambda{|attachment,style| attachment.name.to_s.pluralize },
         :attachment   => lambda{|attachment,style| attachment.name.to_s.pluralize },
         :style        => lambda{|attachment,style| style || attachment.default_style },
         :style        => lambda{|attachment,style| style || attachment.default_style },
       }
       }