authz: Fix logic for repos without external repo set
Created by: tsenart
This commit makes authzFilter
include repositories that have no
ExternalRepoSpec
set when authzAllowByDefault
is true and there are
not external services configured with auth
fields (at the moment,
GitHub and GitLab are only ones).
With this patch, Gitolite repos that were created without external repo set (before Gitolite special chars #2972) can be read by normal users before repo-updater has a chance to sync those repos, and, hence, persisting their external repo field.
Part of https://github.com/sourcegraph/infrastructure/issues/1505
Test plan: go test