code: public static void writeUnixLines(Iterable<? extends CharSequence> lines, CharSink sink)
        throws IOException {
      sink.writeLines(lines, "\n");
    }
docs: Generally we want to avoid {@link CharSink#writeLines(Iterable)} because it uses the OS default
  line separator, but our code always works with Unix line endings regardless of platform. This
  is just like {@link CharSink#writeLines(Iterable)}, but always uses Unix endings.