How to mirror a remote (external) repository when my gitlab is firewalled and can't reach out by itself?

I’m using an internal gitlab-ce on one of my hosts. I want to fix a bug in an OSS project that is not being maintained, so I want to make a local clone of the upstream repository and keep my changes local. My gitlab host is firewalled and can not reach the remote repo itself, so I can’t use the gitlab mirror or import options from the gitlab host itself.

I tried doing a git clone to my laptop from the upstream repository, and then importing that into my local gitlab project. When I did a test checkout from the new project back to my laptop, the new copy arrived without any of the branches, and I couldn’t do a ‘git checkout’ to reach the branch I’m needing to update.

I’ve fiddled with this for several hours already and can’t seem to find the magic that will make the repository in my gitlab contain the same branches as the original. I looked through a number of stackoverflow threads and didn’t find one that matched my situation, either.

Do I need to check out every remote branch manually and re-import them?