Add Matrix to Buildkite pipeline file

[joshedney]

Goal

Reduce the noise in .buildkite/pipeline.yml by using matrix on steps where possible.

Design

Implement matrix on steps that share common setups and do not rely on

Testing

Full CI has been run

[imjoehaines]

Is it possible to reduce the duplication even more by doing something like this?

  - label: ":ruby: Ruby {{ matrix.ruby-version }} unit tests"
    matrix:
      adjustments:
        - with:
          ruby-version: "2.0"
          bundle-version: "1.12.0"
        - with:
          ruby-version: "2.1"
          bundle-version: "1.12.0"
        - with:
          ruby-version: "2.2"
          bundle-version: "1.12.0"
          gemsets: "test sidekiq"
        - with:
          ruby-version: "2.3"
          bundle-version: "1.12.0"
          gemsets: "test sidekiq"
        - with:
          ruby-version: "2.4"
          gemsets: "test sidekiq"
        - with:
          ruby-version: "2.5"
          gemsets: "test sidekiq"
        - with:
          ruby-version: "2.6"
          gemsets: "test sidekiq"
        - with:
          ruby-version: "3.0"
          gemsets: "test sidekiq"
        - with:
          ruby-version: "3.1"
          gemsets: "test sidekiq"
    timeout_in_minutes: 30
    plugins:
      docker-compose#v3.1.0:
        run: ruby-unit-tests
        use-aliases: true
    env:
      RUBY_TEST_VERSION: "{{ matrix.ruby-version }}"
      BUNDLE_VERSION: "{{ matrix.bundle-version }}"
      GEMSETS: "{{ matrix.gemsets }}"
    concurrency: 4
    concurrency_group: "ruby/unit-tests"

[joshedney]

I don't believe so. I've tried a couple of different layouts trying to get the most efficient combination. My understanding is this:

If we had the below matrix

matrix:
  setup:
    version:
      - '2.2'
      - '2.3'
    gemsets:
      - 'test sidekiq'
    bundle_version:
      - '1.12.0'
  adjustments:
    - with:
        version: '2.2'
        gemsets: ''
        bundle_version: '1.12.0'

It would end up running 3 tests in total.

One with version:2.2, gemsets: test sidekiq, bundle_version: 1.12.0

The second with `version: 2.3, gemsets: test sidekiq, bundle_version: 1.12.0'

And the third one would be version: 2.2, gemsets:, bundle_version: 1.12.0

We could add the variations that we'd want and then skip the ones that we know would fail, but we'd then end up with more duplication.

[imjoehaines]

just some small changes, then this looks fine (other than how half-baked the feature is ☹️)

Can you squash merge this so we don't keep the intermediate commits?

[imjoehaines]

This is a duplicate of the step above