Paperclip on rails 1.2.6

environment.rb

# stick this code at the bottom of your config/environment.rb
# (unless, of course, you already have something similar)

initializer_glob = File.join(RAILS_ROOT, "config/initializers/*.rb")
initializers = Dir[initializer_glob].map {|f| File.expand_path(f) }.sort
initializers.each {|f| require f }

paperclip_on_rails_126.rb

# and stick this code into config/initializers/paperclip_on_rails_126.rb

# Paperclip only claims rails 2.1 compatibility, but it seems to mostly work
# with rails 1.2.6.  Where it doesn't, we've put any necessary monkey-patches in
# here.
# If you notice any further bugs, please feel free to comment on or fork this gist.

require 'paperclip/railtie'

module Paperclip
  module CallbackCompatability
    module Rails12
      def self.included(base)
        base.extend(Defining)
        base.send(:include, Running)
      end

      module Defining
        def define_paperclip_callbacks(*args)
          args.each do |callback|
            define_callbacks("before_#{callback}")
            define_callbacks("after_#{callback}")
          end
        end
        def define_callbacks(method)
          class_eval <<-"end_eval"
            def self.#{method}(*callbacks, &block)
              callbacks << block if block_given?
              write_inheritable_array(#{method.to_sym.inspect}, callbacks)
            end
          end_eval
        end
      end

      module Running
        def run_paperclip_callbacks(callback, opts = nil, &blk)
          # The overall structure of this isn't ideal since after callbacks run even if
          # befores return false. But this is how rails 3's callbacks work, unfortunately.
          return false if callback(:"before_#{callback}") == false
          returning(blk.call) do
            callback(:"after_#{callback}")
          end
        end
      end
    end
  end
end

module Paperclip
  def self.included(base)
    base.extend ClassMethods
    base.send :include, Paperclip::CallbackCompatability::Rails12
  end
end

Paperclip::Railtie.insert

module Rails
  def self.root
    RAILS_ROOT
  end
  def self.env
    RAILS_ENV
  end
end

forgot Rails.env in the first revision (it is required by Paperclip::Storage::S3)

Updated gist with recommendation on how to load it via config/initializers