src/vs/editor/common/model/editStack.ts/EditStack/_getOrCreateEditStackElement
class EditStack:	private _getOrCreateEditStackElement(beforeCursorState: Selection[] | null, group: UndoRedoGroup | undefined): EditStackElement {
		const lastElement = this._undoRedoService.getLastElement(this._model.uri);
		if (isEditStackElement(lastElement) && lastElement.canAppend(this._model)) {
			return lastElement;
		}
		const newElement = new SingleModelEditStackElement(nls.localize('edit', "Typing"), 'undoredo.textBufferEdit', this._model, beforeCursorState);
		this._undoRedoService.pushElement(newElement, group);
		return newElement;
	}