private void installBase(String href) {
        if (baseSeen) {
            return;
        }
        baseSeen = true;

        LinkedList<Node> oldStack = stack;
        stack = new LinkedList<>();
        int i = 0;
        for (Node node : oldStack) {
            if (i == 0) {
                stack.addLast(node); // root
            } else if (i == 1) {
                push(href, node.langSpeficied ? node.lang : null,
                        node.rtl ? Direction.RTL : Direction.LTR);
            } else {
                push(node.originalRelative, node.langSpeficied ? node.lang
                        : null, node.rtl ? Direction.RTL : Direction.LTR);
            }
            i++;
        }
    }
-1 at start
0 in html
>=1 in head
-2 situation over
src/nu/validator/xml/BaseUriTracker.java