The current GitHub Actions validation workflow can be improved in several ways.

• It should not run on "pull_request" (OpenJDK repos don't allow this but will transfer results of push runs in forked repositories into status checks of PRs)
• A possibility to trigger the workflow manually via "workflow_dispatch" would be nice
• Updates to a branch should cancel running actions in favor of a new run to save resources
• The workflow script can have less redundant code by using a matrix strategy for the different operating systems that are tested
• Used actions can be version-bumped
• Naming of some steps can be improved
• The test steps and their order can be improved to make the steps more logical and explicit:
  • 1. Build&Test core
  • 2. Start P2 repository
  • 3. Build&Test application
  • 4. Build&Test agent
  • 5. Run spotless
• Use maven option --no-transfer-progress to get less noisy logs