src/vs/workbench/contrib/mergeEditor/browser/model/mapping.ts/DocumentRangeMap/outputLineCount
class DocumentRangeMap:	public get outputLineCount(): number {
		const last = lastOrDefault(this.rangeMappings);
		const diff = last ? last.outputRange.endLineNumber - last.inputRange.endLineNumber : 0;
		return this.inputLineCount + diff;
	}