@Override
    public int compare(Hit left, Hit right) {
        if (left.isMeta() && right.isMeta()) {
            return 0;
        } else if (left.isMeta()) {
            return -1;
        } else if (right.isMeta()) {
            return 1;
        } else {
            return super.compare(left, right);
        }
    }
Ensures that meta hits are sorted before normal hits. All meta hits are
considered equal.

@author Tony Vaagenes
container-search/src/main/java/com/yahoo/search/result/MetaHitsFirstComparator.java