Saving a file to a new name adds a new step into the undo order, so if you save a file to one name, save as to a new name, then undo, it will start saving to the first file again. That is unexpected, so changes to the file source should be tracked separately from the undo state.
Saving a file to a new name adds a new step into the undo order, so if you save a file to one name, save as to a new name, then undo, it will start saving to the first file again. That is unexpected, so changes to the file source should be tracked separately from the undo state.