@VisibleForTesting
  List<Allocation> getUnfinishedAllocations() {
    return completionMap.values().stream()
        .filter(IndexedRemainingUnits::isUnfinished)
        .sorted()
        .map(remainingUnits -> remainingUnits.allocation)
        .collect(Collectors.toList());
  }
Gets a list of the unfinished {@link Allocation}s in the order in which those {@link
Allocation}s were encountered. This can be used to display, for example, currently executing
tasks. The order helps to keep the displayed tasks in a deterministic order (new subtasks
appear below older ones) and not jumbled together in some random order.

@return a list of unfinished {@link Allocation}s
jib-core/src/main/java/com/google/cloud/tools/jib/event/progress/AllocationCompletionTracker.java