@Override
  public Object handle (TaskExecution aTask) throws Exception {
    List<String> chunks = aTask.getList("chunks",String.class);
    logger.debug("{}",chunks);
    File tempFile = File.createTempFile("_chunks", ".txt");
    try {
      try (Writer writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(tempFile, true), "UTF-8"))) {
        for(String chunk : chunks) {
          writer.append(String.format("file '%s'", chunk))
                .append("\n");
        }
      }
      SimpleTaskExecution ffmpegTask = new SimpleTaskExecution();
      List<String> options = Arrays.asList(
        "-y",
        "-f","concat",
        "-safe","0",
        "-i",tempFile.getAbsolutePath(),
        "-c","copy",
        aTask.getRequiredString("outputFile")
      );
      ffmpegTask.set("options", options);
      ffmpeg.handle(ffmpegTask);
    }
    finally {
      FileUtils.deleteQuietly(tempFile);
    }
    return null;
  }
a {@link TaskHandler} implementation which "stitches" together a 
collection of <code>chunks</code> into a single file specified by 
the <code>output</code> property.

@author Arik Cohen
@since Jun 4, 2017
src/main/java/com/creactiviti/piper/taskhandler/media/Vstitch.java