src/vs/editor/browser/widget/diffReview.ts/DiffReview/_findDiffIndex
class DiffReview:	private _findDiffIndex(pos: Position): number {
		const lineNumber = pos.lineNumber;
		for (let i = 0, len = this._diffs.length; i < len; i++) {
			const diff = this._diffs[i].entries;
			const lastModifiedLine = diff[diff.length - 1].modifiedLineEnd;
			if (lineNumber <= lastModifiedLine) {
				return i;
			}
		}
		return 0;
	}