Seed new instances with a sample repository

Created by: chrismwendt

I have a suspicion that external service configuration is a big hurdle to setup. Wouldn't it be great if prospective customers could run a search and see basic code intel working immediately after entering their admin info?

The repository could contain:

• A README with screenshots/videos of Sourcegraph in action
• A file or two for each of the ~6 languages that we have basic code intelligence support for (see https://github.com/sourcegraph/sourcegraph/issues/2035)

I'm not sure how to accomplish this from a technical perspective (Would this be a special case? Would it be part of a default external service? Where would the repository live? Is it baked into the image? etc.).

cc @sqs @nicksnyder @ryan-blunden Let's add this to the list of topics for the meeting about improving the admin onboarding and setup experience