# File lib/fpm/source/npm.rb, line 23
  def make_tarball!(tar_path, builddir)
    tmpdir = "#{tar_path}.dir"
    installdir = "#{tmpdir}/#{::Gem::dir}"
    ::FileUtils.mkdir_p(installdir)
    args = ["gem", "install", "--quiet", "--no-ri", "--no-rdoc",
       "--install-dir", installdir, "--ignore-dependencies", @paths.first]
    safesystem(*args)
    tar(tar_path, ".", tmpdir)

    # TODO(sissel): Make a helper method.
    safesystem(*["gzip", "-f", tar_path])
  end