code: private void addFlagFileOption() {
          String name = "flagfile";
          String shortName = getAndAddUniqueShortName(name);
          String description = "Special flag: file from which to read additional flags"
                  + " (lines starting with # are ignored as comments,"
                  + " and these flags are always processed before those on the command line).";
          flagfileOpt = new Option(shortName, name, true, description);
          flagfileOpt.setRequired(false);
          options.addOption(flagfileOpt);
      }
docs: Adds a special option --flagfile (akin to gflags' flagfile option
  http://gflags.github.io/gflags/#special) that specifies a file from which to read additional
  flags.