GitLab is used only for code review, issue tracking and project management. Canonical locations for source code are still https://gitweb.torproject.org/ https://git.torproject.org/ and git-rw.torproject.org.
If I click on a link and open it with TBA when TBA is closed like here -
It doesn't open in the custom tab and I get this -
But if I first open TBA and click Connect then go and click on the link then it opens up like it should.