Fix selector in getResolvedDiffForCompare()
Created by: lguychard
I've been seeing a lot of 'cannot determine delta info'
Sentry exceptions on github compare pages (eg. https://github.com/DefinitelyTyped/DefinitelyTyped/compare/master...felixfbecker:sinon-spy?expand=1). Turns out the branchElements
selector was outdated.