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.

Tags give the ability to mark specific points in history as being important
Repository has no tags yet.
Use git tag command to add a new one:
git tag -a v1.4 -m 'version 1.4'