def merge other
    unless name == other.name then
      raise ArgumentError,
            "#{self} and #{other} have different names"
    end

    default = Gem::Requirement.default
    self_req  = self.requirement
    other_req = other.requirement

    return self.class.new name, self_req  if other_req == default
    return self.class.new name, other_req if self_req  == default

    self.class.new name, self_req.as_list.concat(other_req.as_list)
  end
#
Merges the requirements of +other+ into this dependency