if (previousExecution.getOutputFilesSnapshot() == null) {
return Collections.<TaskStateChange>singleton(new DescriptiveChange("Output file history is not available.")).iterator();
}
return new AbstractIterator<TaskStateChange>() {
final FileCollectionSnapshot.ChangeIterator<String> changeIterator = outputFilesBefore.iterateChangesSince(previousExecution.getOutputFilesSnapshot());
final ChangeListenerAdapter listenerAdapter = new ChangeListenerAdapter();
@Override
protected TaskStateChange computeNext() {
if (changeIterator.next(listenerAdapter)) {