extensions/git/src/util.ts/uniqBy
export function uniqBy<T>(arr: T[], fn: (el: T) => string): T[] {
	const seen = Object.create(null);

	return arr.filter(el => {
		const key = fn(el);

		if (seen[key]) {
			return false;
		}

		seen[key] = true;
		return true;
	});
}