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commands:
  plugins:enable <gem name>    # would not install, just enable in config
  plugins:disable <gem name>   # disables gem from config, but does not uninstall the gem
  plugins:install <gem name>   # install and enable the gem
  plugins:uninstall <gem name> # uninstall and remove from the config

init.rb

module HerokuConfig
  extend Heroku::Helpers
  
  def self.config_file
    "#{home_directory}/.herogems.yml"
  end
end

YAML.load_file(HerokuConfig.config_file).each do |gem|
  begin
    require gem.gsub!('-', '/')
  rescue LoadError
    $stderr.puts "Can not load: #{gem}"
  end
end