The batching approach will definitely get you most of the way there today. No further changes would be needed.

However, I think it would be great to have the concept of a group-like artifact baked into the gating tooling. For example, there's no way to determine the test results of combined artifacts today. Sure, the results for each artifact can be combined, but what's missing are the results of how those artifacts interact with each other.

Would this be beneficial for the side-tags work?

Hello pingou,
thank you for filing this. At the moment I'm working on a proposal for "group-like" artifact in greenwave. Basically Greenwave won't consider the artifacts passed as a collection of different artifacts, but it will process them as a unique item. Kinda like you proposed for side-tags, but it could be used for more general use cases.
This might solve also the performances issues that we had.

This could improve performance significantly with koji-build-group (side-tags).

Few problems I can think of:

• Greenwave still doesn't have a way to fetch remote rules (gating.yaml files) for separate builds and for the whole group (but this could be available in next release).
• Only the test result for whole group is available (see koji-build-group.test.complete messages in CI Messages repo).
• Fetching a lot of remote rule files for big group can still be a problem and cause timeouts.