Hey Dervish, the AlmaLinux Build System (ALBS) [1][2] is responsible for doing this, and it creates updateinfos using pulp's pulp_rpm plugin [3], which is what the ALBS uses behind the curtains to deal with repositories. As far as I can tell, I believe that pulp_rpm uses the createrepo_c python library [4] to create and manipulate them. For this reason, I'd say that you need to take a look at that library's documentation and figure out things by yourself. There's even an example that shows a basic example here [5], but never tested it myself.
If you already have a valid updateinfo.xml and things don't work, then I'm not sure what's the problem. Hope this helps, and good luck on that! Javi [1] https://build.almalinux.org/ [2] https://github.com/AlmaLinux/albs-web-server [3] https://docs.pulpproject.org/pulp_rpm/ [4] https://pypi.org/project/createrepo-c/ [5] https://github.com/rpm-software-management/createrepo_c/blob/master/examples/python/updateinfo_gen_01.py
