Multiple upstream servers with bundled nginx

Problem to solve

Possibility to use bundled nginx for GitLab HA configurations, e.g. define multiple servers for gitlab-workhorse upstream in /var/opt/gitlab/nginx/conf/nginx.conf.

For Registry server (suitable if the host has only bundled Registry without GitLab application) similar problem solving by adding in gitlab.rb:

registry['enable'] = true
registry_nginx['enable'] = false   # delete /var/opt/gitlab/nginx/conf/gitlab-registry.conf
gitlab_rails['enable'] = false     # delete /var/opt/gitlab/nginx/conf/gitlab-http.conf
nginx['custom_nginx_config'] = "include /var/opt/gitlab/nginx/conf/gitlab-registry-custom.conf;"

But this "hack" isn't suitable for hosts with GitLab app, because we can't disable gitlab_rails and necessary upstream ("gitlab-workhorse") define in /var/opt/gitlab/nginx/conf/nginx.conf.

gitlab-ce~2975006