for {
		select {
		case event := <-wk.dirWatcher.Events:
			// work on a copy of the watchedFiles map, so that we don't interfere
			// with the caller's use of the map
			for path, ft := range wk.getTrackers() {
				if ft.events == nil {
					// tracker has been retired, skip it
					continue
				}

				sum := getHashSum(path)
				if !bytes.Equal(sum, ft.hash) {
					ft.hash = sum

					select {

    @Override
    public Class<ExecuteTaskBuildOperationDetails> getDetailsType() {
        return ExecuteTaskBuildOperationDetails.class;
    }

    @Override
    public List<? extends BuildOperationTracker> getTrackers() {
        return ImmutableList.of(taskOriginTracker, operationResultPostProcessor);
    }

    @Override
    public InternalOperationDescriptor lookupExistingOperationDescriptor(Node node) {

    @Override
    public Class<ExecuteTestBuildOperationType.Details> getDetailsType() {
        return ExecuteTestBuildOperationType.Details.class;
    }

    @Override
    public List<? extends BuildOperationTracker> getTrackers() {
        return ImmutableList.of(taskTracker);
    }

    @Override