In https://gitlab.com/gitlab-org/gitlab/blob/c89a6b4548e42ed446099c992c5359bfe34d1de2/ee/lib/ee/gitlab/checks/diff_check.rb#L23, we check whether the query parameter `protocol` is `web` to determine whether we should validate CODEOWNERS. I think the goal there is to allow merge requests bypass `CODEOWNERS` checks, but prevent direct pushes. If that's the case, we already attempt to detect whether the push is coming from a merge request via `MatchingMergeRequest` in https://gitlab.com/gitlab-org/gitlab/blob/28439ca4b1dd14f22a5a6ad14530f6bf1046f8bc/lib/gitlab/checks/branch_check.rb#L102. Maybe we should be using that instead of this magic query parameter value? Or maybe we should be more explicit and instead of the obscure `protocol=web` field use the query parameter `merge_request=true`.