Refactor to ease development of tasks in external Git repositories

[michaelsauter]

Provide Go package(s) allowing to develop tasks easily in external Git repositories. Eventually, the goal is to extract the build / package / deploy tasks from this repo and have them in separate Git repositories with independent lifecycle.

Package tektontaskrun provides ODS Pipeline independent functionality to run Tekton tasks in a KinD cluster. The code is mostly copied from test/tasks/common_test.go and pkg/tasktesting. Package odstasktest builds on top of tektontaskrun and provides ODS Pipeline specific functionality to run ODS Pipeline tasks (e.g. installing ODS Pipeline, starting Nexus, etc.).

As a side-effect, the new approach allows to just run the Go tests without requiring to prepare any state upfront. All dependencies will be taken care of by the Go packages. As an example, here is how an external repo can use this:

// main_test.go
import (
	ott "github.com/opendevstack/ods-pipeline/pkg/odstasktest"
	ttr "github.com/opendevstack/ods-pipeline/pkg/tektontaskrun"
)

var namespaceConfig *ttr.NamespaceConfig

func TestMain(m *testing.M) {
	cc, err := ttr.StartKinDCluster(
		ttr.LoadImage(ttr.ImageBuildConfig{
			Dockerfile: "build/images/Dockerfile.go-toolset",
			ContextDir: rootPath,
		}),
	)
	if err != nil {
		log.Fatal("Could not start KinD cluster: ", err)
	}
	nc, cleanup, err := ttr.SetupTempNamespace(
		cc,
		ott.InstallODSPipeline(),
		ttr.InstallTaskFromPath(
			filepath.Join(rootPath, "build/tasks/ods-pipeline-v1-go-build.yaml"),
			nil,
		),
	)
	if err != nil {
		log.Fatal("Could not setup temporary namespace: ", err)
	}
	defer cleanup()
	namespaceConfig = nc
	os.Exit(m.Run())
}

// go_build_test.go
import (
	ott "github.com/opendevstack/ods-pipeline/pkg/odstasktest"
	ttr "github.com/opendevstack/ods-pipeline/pkg/tektontaskrun"
)
func TestBuildGoTask(t *testing.T) {
	if err := ttr.RunTask(
                ttr.InNamespace(namespaceConfig.Name),
		ttr.UsingTask("ods-pipeline-v1-go-build"),
		ttr.WithStringParams(map[string]string{
			"go-os":       runtime.GOOS,
			"go-arch":     runtime.GOARCH,
			"cache-build": "false",
		}),
		withGoWorkspace(t, "go-sample-app"),
		ttr.AfterRun(func(config *ttr.TaskRunConfig, run *tekton.TaskRun) {
			wd := config.WorkspaceConfigs["source"].Dir
			cmd := exec.Command(wd + "/docker/app")
			b, err := cmd.Output()
			if err != nil {
				t.Fatal(err)
			}
			goProverb := "Don't communicate by sharing memory, share memory by communicating."
			if string(b) != goProverb {
				t.Fatalf("Got: %+v, want: %+v.", string(b), goProverb)
			}

			ott.AssertFilesExist(t, wd,
				"docker/Dockerfile",
				"docker/app",
				filepath.Join(pipelinectxt.LintReportsPath, "report.txt"),
				filepath.Join(pipelinectxt.XUnitReportsPath, "report.xml"),
				filepath.Join(pipelinectxt.CodeCoveragesPath, "coverage.out"),
			)
		}),
	); err != nil {
		t.Fatal(err)
	}
}

...

This is still very much in progress.

For two examples using this PR, see https://github.com/BIX-Digital/ods-pipeline-go and https://github.com/BIX-Digital/ods-pipeline-sonar.

Closes #163

Tasks:

• Updated design documents in docs/design directory or not applicable
• Updated user-facing documentation in docs directory or not applicable
• Ran tests (e.g. make test) or not applicable
• Updated changelog or not applicable