Fix N+1 Gitaly calls in /api/v4/projects/:id/issues
This is a follow-up from https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/31938.
In GitLab 9.0,
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9661 removed the
subscribed flag from the API when the user requested a list of issues
or merge requests since calculating this value triggers extensive
In GitLab 12.0 via a4fbf39e, we accidentally reintroduced this
performance regression by changing
entities.rb. This showed up as a Gitaly N+1 issue since the Markdown
processing would attempt to extract a commit if it detected a regex
that matched a commit.
We restore the prior behavior by once again removing the
for the bulk list of issues and merge requests and add a test to ensure
they aren't reintroduced.