patagonicus/gitlab repository overview

This is a workaround for #2889⁠ for people using sameersbn's docker images⁠. All it does is set max_allowed_packet in my.cnf to 512MB.

Note that you must use the modified mysql image to make it possible to create large merge requests and you need the modified GitLab image if you want to create backups (otherwise mysqldump will complain about packets being too large).