GitLab UI only, for existing git repos?

###Is this possible and/or feasible?
I have many git repos on my system. I want to use the GitLab UI and its functionalities on these repos without importing them to GitLab. This way I can make modifications with usual git commands and it will be reflected in GitLab UI.

If not supported out of the box, can it be done with some coding effort?

The closest you could do is change the default location git repos are stored.

See https://gitlab.com/gitlab-org/omnibus-gitlab/blob/629def0a7a26e7c2326566f0758d4a27857b52a3/README.md#storing-git-data-in-an-alternative-directory

So ultimately you should name the top level dir where your repos are located repositories and set the git_data_dir variable to the parent of repositories. But then, after running reconfigure it would change their permissions and ownership.

That’s if you use the package. You might get away with it easier with the manual installation.