class Bundler::Runtime

def prune_cache
  FileUtils.mkdir_p(cache_path)
  resolve = @definition.resolve
  cached  = Dir["#{cache_path}/*.gem"]
  cached = cached.delete_if do |path|
    spec = Gem::Format.from_file_by_path(path).spec
    resolve.any? do |s|
      s.name == spec.name && s.version == spec.version && !s.source.is_a?(Bundler::Source::Git)
    end
  end
  if cached.any?
    Bundler.ui.info "Removing outdated .gem files from vendor/cache"
    cached.each do |path|
      Bundler.ui.info "  * #{File.basename(path)}"
      File.delete(path)
    end
  end
end