src/vs/editor/browser/widget/diffEditorWidget.ts/DiffEditorWidget/_getEquivalentLineForOriginalLineNumber
class DiffEditorWidget:	private _getEquivalentLineForOriginalLineNumber(lineNumber: number): number {
		const lineChange = this._getLineChangeAtOrBeforeLineNumber(lineNumber, (lineChange) => lineChange.originalStartLineNumber);

		if (!lineChange) {
			return lineNumber;
		}

		const originalEquivalentLineNumber = lineChange.originalStartLineNumber + (lineChange.originalEndLineNumber > 0 ? -1 : 0);
		const modifiedEquivalentLineNumber = lineChange.modifiedStartLineNumber + (lineChange.modifiedEndLineNumber > 0 ? -1 : 0);
		const lineChangeOriginalLength = (lineChange.originalEndLineNumber > 0 ? (lineChange.originalEndLineNumber - lineChange.originalStartLineNumber + 1) : 0);
		const lineChangeModifiedLength = (lineChange.modifiedEndLineNumber > 0 ? (lineChange.modifiedEndLineNumber - lineChange.modifiedStartLineNumber + 1) : 0);


		const delta = lineNumber - originalEquivalentLineNumber;

		if (delta <= lineChangeOriginalLength) {
			return modifiedEquivalentLineNumber + Math.min(delta, lineChangeModifiedLength);
		}

		return modifiedEquivalentLineNumber + lineChangeModifiedLength - lineChangeOriginalLength + delta;
	}