@Override
    public int compare(Path o1, Path o2) {
      return Long.compare(getTS(o1), getTS(o2));
    }
Comparator used to compare WAL files together based on their start time. Just compares start
times and nothing else.
hbase-server/src/main/java/org/apache/hadoop/hbase/wal/AbstractFSWALProvider.java