docs: @Override
      public FileBuilder addFile(Path source, Path target) throws IOException
      {
          checkTarget(target);
          FileBuilder fb =  new FileBuilder();
          fb.target = target;
          fb.size = (int) Files.size(source);
          try (FileChannel fc = FileChannel.open(source, READ))
          {
              fb.content = fc.map(FileChannel.MapMode.READ_ONLY, 0, fb.size);
          }
          FileTime fileTime = Files.getLastModifiedTime(source);
          fb.time = (int)fileTime.to(TimeUnit.SECONDS);
          fb.compressFilename();
          fileBuilders.add(fb);
          return fb;
      }