Exclude gems in heroku Cedar. Heroku will ignore :development and :test by default, but not other groups (such as :cucumber). Previous Bamboo stack let you define BUNDLE_WITHOUT, but it doesn't work anymore on Cedar.

bundler.rb

# Put this code in some file and require it at the beginning of your Gemfile
# Then you can list the groups to exclude from heroku. E.g:
#
#   exclude_in_heroku :cucumber, :development, :test
#
# Based on this post by Matt Campbell: http://soupmatt.com/fixing-bundlewithout-on-heroku-cedar,
# which is based in an idea by @grosser. All the credits to them.
module Bundler
  class Dsl
    old_group = instance_method(:group)

    def exclude_in_heroku(*groups)
      @gems_to_exclude = groups
    end

    def gems_to_exclude
      @gems_to_exclude ||= []
    end

    define_method(:group) do |*groups, &block|
      should_exclude = groups.find{|group| gems_to_exclude.include?(group)}
      groups = (should_exclude && ENV['HOME'].gsub('/', '') == 'app') ? 'test' : groups
      old_group.bind(self).(*groups, &block)
    end
  end
end