def unpack(file, dest)
      ::Zip::ZipFile.foreach(file) do |zentry|
        epath = "#{dest}/#{zentry}"
        dirname = File.dirname(epath)
        FileUtils.mkdir_p(dirname) unless File.exists?(dirname)
        zentry.extract(epath) unless File.exists?(epath)
      end
    end
def unpack(file, dest)
      ::Zip::ZipFile.foreach(file) do |zentry|
        epath = "#{dest}/#{zentry}"
        dirname = File.dirname(epath)
        FileUtils.mkdir_p(dirname) unless File.exists?(dirname)
        zentry.extract(epath) unless File.exists?(epath)
      end
    end
Unpack a zip +file+ to directory +dest+.