src/vs/workbench/contrib/mergeEditor/browser/model/rangeUtils.ts/lengthOfRange
export function lengthOfRange(range: Range): LengthObj {
	if (range.startLineNumber === range.endLineNumber) {
		return new LengthObj(0, range.endColumn - range.startColumn);
	} else {
		return new LengthObj(range.endLineNumber - range.startLineNumber, range.endColumn - 1);
	}
}