Bundeling the same project with rails 2 and rails 3 (multiple gem versions but same gemfile) ``` ln -s Gemfile Gemfile.rails3 bundle BUNDLE_GEMFILE=Gemfile.rails3 bundle ``` using vendor/cache ? -> save disc space: ``` cd vendor/cache_rails3 ls ../cache | pru '%x{rm #{self} && ln -s ../cache/#{self}} if File.exist?(self)' ```

Gemfile

rails3 = ENV["BUNDLE_GEMFILE"].to_s.include?("rails3")

...

if rails3
  # make bundler use a different cache dir
  class << Bundler
    def app_cache
      root.join("vendor/cache_rails3")
    end
  end

  Bundler::Runtime.class_eval do
    def cache_path
      Bundler.app_cache
    end
  end
end