Migrate Rails project from config.gem to Bundler

gistfile1.txt

Steps to migrate a Rails 2.3 project to bundler.

1. Install bundler
  
  gem install bundler

2. Remove existing vendor gems directory
  
  rm -rf vendor/gems

3. Remove all config.gem commands from config/environment.rb

4. Create Gemfile in RAILS_ROOT. Example:

  # disable_system_gems uses the rubygems library, but prevents system gems
  # from being loaded; only gems that are bundled will be available to your
  # application. This option guarantees that dependencies of your 
  # application will be available to a remote system.
  disable_system_gems

  bundle_path "vendor/bundler_gems"
  clear_sources
  source "http://gemcutter.org"

  gem "rails", "2.3.5"

  gem "RedCloth"
  gem "mysql"
  gem "paperclip"
  gem "will_paginate"

  only :test do
    gem "rspec"
    gem "rspec-rails"
  end

5. Create a config/preinitializer.rb

  # Required for bundler
  bundler_env = File.expand_path("#{File.dirname(__FILE__)}/../vendor/bundler_gems/environment.rb")

  if File.exists?(bundler_env)
    require bundler_env
  else
    puts "*** Gems not Bundled *** "
    puts "You must first install Bundler, gem install bundler, and then bundle gems for this project"
    puts "From rails root - gem bundle, or for OSX 10.6, ARCHFLAGS=\"-arch x86_64\" gem bundle"
    exit(1)
  end

6. Add Bundler.require_env to the bottom of each config/environments/* file

7. Bundle gems
  
  gem bundle
  
or on OSX 10.6 (archflags required for MySQL)

  ARCHFLAGS=\"-arch x86_64\" gem bundle
  
8. Add lines to .gitignore that ignores bundled gems directory, but keep gem cache:

  # Used for bundler, only keep the cached directory
  bin/*
  vendor/bundler_gems/*
  !vendor/bundler_gems/ruby/1.8/cache/

9. Add capistrano deploy tasks

  namespace :bundler do
    task :install do
      run("gem install bundler --source=http://gemcutter.org")
    end

    task :symlink_vendor, :roles => :app, :except => { :no_release => true } do
      shared_gems = File.join(shared_path, 'vendor/gems/ruby/1.8')
      release_gems = "#{release_path}/vendor/gems/ruby/1.8"
      # if you don't commit your cache, add cache to this list
      %w(gems specifications).each do |sub_dir|
        shared_sub_dir = File.join(shared_gems, sub_dir)
        run("mkdir -p #{shared_sub_dir} && mkdir -p #{release_gems} && ln -s #{shared_sub_dir} #{release_gems}/#{sub_dir}")
      end
    end
 
    task :bundle_new_release, :roles => :app, :except => { :no_release => true }  do
      bundler.symlink_vendor
      # if you don't commit your cache, remove --cached from this line
      run("cd #{release_path} && gem bundle --only #{rails_env} --cached")
    end
  end

  # hook into capistrano's deploy task
  after 'deploy:update_code', 'bundler:bundle_new_release'