title: Qt Clear Undo History in a QTextEdit/QPlainTextEdit?
body: <p>I have a QPlainTextEdit and I'm building a progress dialog for it when opening large files. Rather than using setText, I want to add one line of text at a time by using QTextCursor.insertText. The problem is that when I do it this way, I can undo each line that was added... is there a way to clear the undo history?</p>