I recently had to migrate over 70 repositories from gitlab to bitbucket. There are import tools provided by providers but they require access to each other in order for them to work. Because the providers we were using could not visibly see each other over the web without being connected to the same VPN this was not an option.

A nice little workaround to get all information from a git repository can be found on my public github here: https://github.com/matjamesymj/git-migration.