class Gem::Specification

def traverse trail = [], visited = {}, &block
  trail.push(self)
  begin
    dependencies.each do |dep|
      next unless dep.runtime?
      dep.to_specs.each do |dep_spec|
        next if visited.has_key?(dep_spec)
        visited[dep_spec] = true
        trail.push(dep_spec)
        begin
          result = block[self, dep, dep_spec, trail]
        ensure
          trail.pop
        end
        unless result == :next
          spec_name = dep_spec.name
          dep_spec.traverse(trail, visited, &block) unless
            trail.any? { |s| s.name == spec_name }
        end
      end
    end
  ensure
    trail.pop
  end
end