@Override
    public int compareTo(IndexedRemainingUnits otherIndexedRemainingUnits) {
      return index - otherIndexedRemainingUnits.index;
    }
Remaining progress units until completion. This can be shared across multiple threads and
should be updated atomically.
jib-core/src/main/java/com/google/cloud/tools/jib/event/progress/AllocationCompletionTracker.java