src/vs/workbench/contrib/mergeEditor/browser/model/mapping.ts/LineRangeMapping/extendInputRange
class LineRangeMapping:	public extendInputRange(extendedInputRange: LineRange): LineRangeMapping {
		if (!extendedInputRange.containsRange(this.inputRange)) {
			throw new BugIndicatingError();
		}

		const startDelta = extendedInputRange.startLineNumber - this.inputRange.startLineNumber;
		const endDelta = extendedInputRange.endLineNumberExclusive - this.inputRange.endLineNumberExclusive;
		return new LineRangeMapping(
			extendedInputRange,
			new LineRange(
				this.outputRange.startLineNumber + startDelta,
				this.outputRange.lineCount - startDelta + endDelta
			)
		);
	}