private void parseCommentLine(Matcher commentMatch) {
        if (!comment.isEmpty()) comment += "\n";
        String addition = commentMatch.group(1);
        if (addition.isEmpty()) addition = " ";
        comment += addition;
    }
Parses one line from def-file and adds it to the tree.
TODO: Method too long!

@param root     The root CNode in the tree.
@param line     A line from the def-file.
@param nd       A NormalizedDefinition object
@throws IllegalArgumentException upon error in line.
configgen/src/main/java/com/yahoo/config/codegen/DefParser.java