Satellites for projects that were located in the root namespace needs to be recreated once they've been migrated to the creator’s namespace during the upgrade process.

This can be achieved by running the sudo -u git -H bundle exec rake gitlab:satellites:create RAILS_ENV=production during the update process.

The command has been added to the 5.4 to 6.0 update doc.

As a consequence on the namespaces change from 5.4 to 6.0, after upgrade
lots of links on the dashboard were not working (pointing to projects
without the group part on the url).
Also, after upgrading to 6.0-stable, the network (branch history) function
does not work. The progress bar rotates forever, but the network graph cannot
be generated.

Clearing redis cache fixes those issues.