setDocumentProvider(new FileDocumentProvider());

public boolean isDirty() {
    return dirty;
}

OperationHistoryFactory.getOperationHistory().addOperationHistoryListener(e -> {
    if(e.getOperation().hasContext(undoContext)) {
        // if there is no more operation to undo
        if(!OperationHistoryFactory.getOperationHistory().canUndo(undoContext)) {
            dirty = false;
            firePropertyChange(IEditorPart.PROP_DIRTY);
        }
    }
});