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

@@ -117,18 +117,21 @@ module Paperclip
     # necessary.
     def self.interpolations
       @interpolations ||= {
-        :rails_root => lambda{|attachment,style| RAILS_ROOT },
-        :class      => lambda{|attachment,style| attachment.instance.class.to_s.pluralize },
-        :basename   => lambda do |attachment,style|
+        :rails_root   => lambda{|attachment,style| RAILS_ROOT },
+        :class        => lambda{|attachment,style| attachment.instance.class.to_s.pluralize },
+        :basename     => lambda do |attachment,style|
           attachment.original_filename.gsub(/\.(.*?)$/, "")
         end,
-        :extension  => lambda do |attachment,style| 
+        :extension    => lambda do |attachment,style| 
           ((style = attachment.styles[style]) && style.last) ||
           File.extname(attachment.original_filename).gsub(/^\.+/, "")
         end,
-        :id         => lambda{|attachment,style| attachment.instance.id },
-        :attachment => lambda{|attachment,style| attachment.name.to_s.pluralize },
-        :style      => lambda{|attachment,style| style || attachment.default_style },
+        :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 },
+        :style        => lambda{|attachment,style| style || attachment.default_style },
       }
     end