.gitignore

.bundle/environment.rb
bundler_gems

boot.rb

class Rails::Boot
  def run
    load_initializer
    extend_environment
    Rails::Initializer.run(:set_load_path)
  end
 
  def extend_environment
    Rails::Initializer.class_eval do
      old_load = instance_method(:load_environment)
      define_method(:load_environment) do
        Bundler.require :default, Rails.env
        old_load.bind(self).call
      end
    end
  end
end

deploy.rb

namespace :bundler do
  task :bundle_new_release do
    run("cd #{release_path} && bundle install")
  end
end

after 'deploy:update_code', 'bundler:bundle_new_release'

Gemfile

source "http://rubygems.org"

gem "rails", "2.3.5", :require => nil
gem "mysql", "2.8.1"

group :test do
  gem "shoulda", "2.10.3"
  gem "factory_girl", "1.2.3"
  gem "fcoury-matchy", "0.4.0", :require => "matchy"
  gem "rcov", "0.9.7.1"
  gem "mocha", "0.9.8"
  gem "metric_fu", "1.3.0"
end

preinitializer.rb

begin
  # Require the preresolved locked set of gems.
  require File.expand_path('../../.bundle/environment', __FILE__)
rescue LoadError
  # Fallback on doing the resolve at runtime.
  require "rubygems"
  require "bundler"
  Bundler.setup
end

test.rb

Bundler.require(:test)