gistfile1.txt

module M0
  def foo
    puts 'M2::foo'
  end
end

module M1
  include M0

  def self.included(model)
    def foo
      puts 'M1::foo'
    end
  end
end

class C1
  include M1
end

class C2 < C1
end

C1.new.foo
C2.new.foo