Epic: Promotion of releases between environments for GitOps

[gianfranco-l]

User story:
As a developer, I want to have a process to implement promotion of releases between environments so that I can ensure smooth quality assurance on my applications before releasing them into production environment

Marcel research on the topic:
Currently, GitOps does not define how it is supposed to work to promote releases.
Some resources and various perspectives on the topic:

• https://codefresh.io/about-gitops/pains-gitops-1-0/ -> undefined process for release promotion
• https://www.gitops.tech/#how-does-gitops-handle-dev-to-prod-propagation -> dev to prod is your problem, not gitops
• https://livebook.manning.com/book/gitops-and-kubernetes/chapter-3/94 -> separation from dev to prod either through branches or folders, no automation
• https://www.reddit.com/r/GitOps/comments/ljlqxa/how_do_you_promote_code_to_environments/ -> discussion on the same issue, no solution recommended
• https://github.com/freiheit-com/kuberpult -> posted earlier, used by customer -> simply copies code around to achieve promotion
• https://codefresh.io/about-gitops/branches-gitops-environments/ -> codefresh says "don't use branches, use folders" does not elaborate HOW
• Best practices for promotion between clusters argoproj/argo-cd#5667 -> giant discussion in Argo about the exact issue
• https://en.sokube.ch/post/promoting-changes-and-releases-with-gitops -> very in depth article describing different solution approaches
• there is also Kubevela and Open Application Model (OAM)

Update June 8th:
Flux v0.31 introduces support promotion of HelmReleases via GitHub actions between environments.
Use case description here, full release notes here

Update July 13th: Scope refinement below

TODO

• Feature: environments gitops-template#41
• https://github.com/giantswarm/giantswarm/issues/22593
• create platform releases using the new app-operator with config lists
• add multi-base example to gitops-template repo based on the stage and region environment cluster templates
• Documentation for customer
• Announce to the customer

Related (?): KaaS Staged Deployments #620

[gianfranco-l]

closing this ticket as this was implemented within the scope of this. There are some missing docs to be produced which are in the scope of this ticket.