What setup does enable git namespaces?

Running GitLab Community edition I found that every time I try to use git namespaces, GitLab ignores my all my requests and throws all changes to the default (unnamed) namespace. What do I need to do to make GitLab not depriving this piece of git standard functionality?
When mentioning ‘namespace’ I mean git --namespace=my_namespace option, also activated by GIT_NAMESPACE=my_namespace shell variable.

When testing locally, namespaces were working correctly (tested for push, pull, clone, fetch git commands) and passing a wrong namespace caused an expected fatal: Remote branch master not found in upstream origin. But when I pass any namespace to GitLab: correct, wrong, none - I GitLab seems to use just a single namespace. It ignores any namespace argument on clone, pull and fetch. I have no access to my organization GitLab instance, so I can’t check if GitLab not interferes the creation of `refs/namespaces/’ directory with all namespaces contained inside.

What shall I do to make GitLab passing git commands completely? It is a git functionality and I can’t imagine how it can be a part of a paid subscription - if it was, it would be more effective to disable git pull command :grinning: