/**
* Adds a hyperlink for a single reference.
*/
void processRef(Ref ref, NBinding nb) {
String path = ref.getFile();
StyleRun link = new StyleRun(StyleRun.Type.LINK, ref.start(), ref.length());
link.message = nb.getQname();
link.url = toURL(nb, path);
if (link.url != null) {
addFileStyle(path, link);
}