class Gem::DependencyResolver::APISet

def prefetch(reqs)
  names = reqs.map { |r| r.dependency.name }
  needed = names.find_all { |d| !@data.key?(d) }
  return if needed.empty?
  u = URI.parse "http://rubygems.org/api/v1/dependencies?gems=#{needed.join ','}"
  str = Net::HTTP.get(u)
  Marshal.load(str).each do |ver|
    @data[ver[:name]] << ver
  end
end