code: private void writeBadManifestEntry(PrintWriter writer, File f, BadFeature bf) {
          writer.write(f.getAbsolutePath()); // 0
          writer.write(FeatureDefinitionUtils.SPLIT_CHAR);
          writer.write(String.valueOf(bf.lastModified)); // 1
          writer.write(FeatureDefinitionUtils.SPLIT_CHAR);
          writer.write(String.valueOf(bf.length)); // 2
      }
docs: Write the data to the cache. This should stay in sync
  with {@link #updateBadManifestCache(String)}, which does the reading.
  
  @param writer
  @param f
  @param bf
  @see #updateBadManifestCache(String)