@Override
	synchronized void clearUndo(boolean notifyListeners) {
		if (!undoList.isEmpty() || !redoList.isEmpty()) {

			undoList.clear();
			redoList.clear();

			for (DomainObjectTransactionManager mgr : domainObjectTransactionManagers) {
				mgr.clearUndo(false);
			}
			if (notifyListeners) {
				notifyUndoableListeners();
			}
		}
	}
Returns the undo stack depth.
(The number of items on the undo stack)
This method is for JUnits.
@return the undo stack depth
Ghidra/Framework/Project/src/main/java/ghidra/framework/data/SynchronizedTransactionManager.java