Documentation for `repositoryQuery` in GitHub default configuration is wrong

Created by: mrnugget

The current defaultConfig for GitHub contains this documentation and default value for repositoryQuery:

https://github.com/sourcegraph/sourcegraph/blob/5632b59b90bd7de7430ca91d0de7e9ca0ea33423/web/src/site-admin/externalServices.tsx#L197-L200

The problem is that the documentation (An array of strings specifying [...]) describes the repos attribute documented here: https://docs.sourcegraph.com/admin/external_service/github#configuration

If you follow the documentation (as I did) and put in, for example, ["sourcegraph/sourcegraph"] you end up with something completely different than expected.

This default configuration is the result of multiple commits. https://github.com/sourcegraph/sourcegraph/commit/da3743ece358fbe6709f07e95d5fd97bd554e047 by @tsenart and https://github.com/sourcegraph/sourcegraph/commit/d2b0714b293d0e916dd7ae0bb06f8dc59d1d606e by @sqs. The last commit that touched this part and removed the repos attribute from the default configuration is this one by @tsenart.

What are your opinions on this? I'm not sure I get all of the reasons for the changes and why things have been added/removed.

But since the default configuration is rather unhelpful (documentation is misleading and you don't have any examples included) I think we now have two options:

1. Change the documentation to correctly describe repositoryQuery
2. Re-add repos so users know how to add single repos to the configuration

Opinions? :)