svoid gzip2xz(File gzInFile, xzOutFile) {
  printFileInfo("Converting to .xz", gzInFile);
  long time = sysNow();
  copyStreamAndCloseAll(
    gzipInputStream(gzInFile),
    xzOutputStream(xzOutFile));
  printFileInfo("Converted in " + renderElapsedTimePleasantly_100ms(sysNow()-time), xzOutFile);
}