"View repository on Sourcegraph" button will always show if repo exists on sourcegraph.com, but then link to configured instance (where it 404s)

Created by: felixfbecker

resolveRev() is used by the "view repo on sourcegraph" button to check for the repos existence. However, resolveRev() calls into queryGraphQL(), which has logic to retry the requests automatically on sourcegraph.com if it fails on the configured instance. This low-level magic retry logic is dangerous - if the repo is on a different instance, we need to explicitly detect that early on, then pass the instance URL of that repo around so we don't retry all the time.