Bundler setup for Rails 2.3.x apps

boot.rb

require 'rubygems'
require 'bundler'

RAILS_ROOT = "#{File.dirname(__FILE__)}/.." unless defined?(RAILS_ROOT)

module Rails
  class << self
    def booted?
      defined? Rails::Initializer
    end

    def vendor_rails?
      File.exist?("#{RAILS_ROOT}/vendor/rails")
    end

    def preinitialize
      load(preinitializer_path) if File.exist?(preinitializer_path)
    end

    def preinitializer_path
      "#{RAILS_ROOT}/config/preinitializer.rb"
    end
  end
end

Bundler.setup
Rails.preinitialize
require 'initializer'

Rails::Initializer.class_eval do
  alias old_load_gems load_gems
  # require gems that are Rails plugins
  def load_gems
    Bundler.require(:plugins)
  end
end

Rails::Initializer.run(:set_load_path)

environment.rb

require File.expand_path('../boot', __FILE__)

## add this line:
Bundler.require(:default, RAILS_ENV)

Rails::Initializer.run do |config|
  ...
end

Gemfile.rb

## example Gemfile
source :rubygems

group :rails do
  gem 'rake', '< 0.9', :require => nil
  gem 'rails', '~> 2.3.5', :require => nil
  gem 'builder', '~> 2.1.2'
  gem 'memcache-client', '>= 1.7.4', :require => nil
  gem 'tzinfo', '~> 0.3.12'
  gem 'i18n', '>= 0.1.3'
  gem 'tmail', '~> 1.2.3'
  gem 'text-format', '>= 0.6.3', :require => 'text/format'
end

# ... normal gems here ...

# put rails plugins in this group:
group :plugins do
  gem 'will_paginate', '~> 2.3.16'
  gem 'hoptoad_notifier', '~> 2.2.2', :require => 'hoptoad_notifier/rails'
  gem 'thinking-sphinx', '~> 1.3.15', :require => 'thinking_sphinx'
  gem 'paperclip', '~> 2.3.1.1'
  gem 'newrelic_rpm', '~> 2.10.6'
end