gdsl.rb

class DSL < BasicObject
  RUBY_VERSION = ::RUBY_VERSION

  attr_reader :envs

  def initialize
    @envs = ::Hash.new { |h, k| h[k] = [] }
    @groups = [:default]
  end

  def method_missing(*args)
    ::Kernel.p(args)
  end

  def source(name, &block)
    @source = name
    yield if block
  end

  def group(*names, &block)
    @groups = names || [:default]
    yield if block
  end

  def gem(name, *args)
    @groups.each do |group|
      @envs[group] << [@source, name, args]
    end
  end
end

require 'pp'

dsl = DSL.new
dsl.instance_eval(File.read('Gemfile'))
pp dsl.envs