code: public static CharSink asCompressedCharSink(File f, Charset charSet) throws IOException {
      return asCompressedByteSink(f).asCharSink(charSet);
    }
docs: Just like {@link Files#asCharSink(java.io.File, java.nio.charset.Charset,
  com.google.common.io.FileWriteMode...)}, but decompresses the incoming data using GZIP.