*: add auto-gen for codegen scripts

[fanminshi]

auto-gen codegen scripts.

[fanminshi]

Manual Test:

func TestCodeGen(t *testing.T) {
	buf := &bytes.Buffer{}
	if err := renderBoilerplateFile(buf, "play"); err != nil {
		t.Error(err)
		return
	}
	if err := ioutil.WriteFile("./boilerplate.go.txt", buf.Bytes(), 0744); err != nil {
		t.Error(err)
	}

	buf = &bytes.Buffer{}
	if err := renderUpdateGeneratedFile(buf, "github.com/coreos/play", "play", "v1alpha1"); err != nil {
		t.Error(err)
		return
	}
	if err := ioutil.WriteFile("./update-generated.sh", buf.Bytes(), 0744); err != nil {
		t.Error(err)
	}
}

Output:

// boilerplate.go.txt
/*
Copyright YEAR The play Authors

Commercial software license.
*/

# update-generated.sh
#!/usr/bin/env bash

set -o errexit
set -o nounset
set -o pipefail

DOCKER_REPO_ROOT="/go/src/github.com/coreos/play"
IMAGE=${IMAGE:-"gcr.io/coreos-k8s-scale-testing/codegen"}

docker run --rm \
  -v "$PWD":"$DOCKER_REPO_ROOT" \
  -w "$DOCKER_REPO_ROOT" \
  "$IMAGE" \
  "/go/src/k8s.io/code-generator/generate-groups.sh"  \
  "all" \
  "github.com/coreos/play/pkg/generated" \
  "github.com/coreos/play/pkg/apis" \
  "play:v1alpha1" \
  --go-header-file "./hack/codegen/boilerplate.go.txt" \
  $@
.

[fanminshi]

cc/ @hongchaodeng @hasbro17

[hongchaodeng]

LGTM

Just to make sure, this build file will not be generated at new, but at generate k8s, right?

[fanminshi]

@hongchaodeng depends on how we going to run the script. we can decided that later on when to run this script.