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.
Apparently NSS does not automatically realize that its SSL sockets are nonblocking when you construct them around a nonblocking TCP socket. You have to make them nonblocking yourself.
Found while investigating #40018 (closed). Root cause of #40018 (closed).