Refactor kubecross retrieval logic

We now introduce a new `kubecross` package which provides a new API for
retrieving the kubecross version for the default as well as a specific
branch. This API will be re-used to set the `KUBE_CROSS_VERSION_LATEST`
substitution, which is being used to build the `krel` binary before
building the actual release.

Signed-off-by: Sascha Grunert <sgrunert@redhat.com>

gcb/release/cloudbuild.yaml

@@ -33,7 +33,7 @@ steps:
     echo "Checking out ${_TOOL_REF}"
     git checkout ${_TOOL_REF}
 
-- name: k8s.gcr.io/releng/releng-ci:v0.5.0
+- name: gcr.io/k8s-staging-releng/k8s-cloud-builder:${_KUBE_CROSS_VERSION_LATEST}
   dir: "go/src/k8s.io/release"
   env:
   - "GOPATH=/workspace/go"

gcb/stage/cloudbuild.yaml

@@ -33,7 +33,7 @@ steps:
     echo "Checking out ${_TOOL_REF}"
     git checkout ${_TOOL_REF}
 
-- name: k8s.gcr.io/releng/releng-ci:v0.5.0
+- name: gcr.io/k8s-staging-releng/k8s-cloud-builder:${_KUBE_CROSS_VERSION_LATEST}
   dir: "go/src/k8s.io/release"
   env:
   - "GOPATH=/workspace/go"

pkg/announce/announce.go

@@ -25,11 +25,10 @@ import (
 
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
-
-	"k8s.io/release/pkg/git"
-	"k8s.io/release/pkg/release"
 	"sigs.k8s.io/release-utils/command"
 	"sigs.k8s.io/release-utils/util"
+
+	"k8s.io/release/pkg/kubecross"
 )
 
 const (
@@ -168,14 +167,14 @@ func getGoVersion(tag string) (string, error) {
 		return "", errors.Wrap(err, "parse version tag")
 	}
 
-	kubecrossBranches := []string{
-		fmt.Sprintf("release-%d.%d", semver.Major, semver.Minor),
-		git.DefaultBranch,
-	}
-
-	kubecrossVer, err := release.GetKubecrossVersion(kubecrossBranches...)
+	branch := fmt.Sprintf("release-%d.%d", semver.Major, semver.Minor)
+	kc := kubecross.New()
+	kubecrossVer, err := kc.ForBranch(branch)
 	if err != nil {
-		return "", errors.Wrap(err, "get kubecross version")
+		kubecrossVer, err = kc.Latest()
+		if err != nil {
+			return "", errors.Wrap(err, "get kubecross version")
+		}
 	}
 
 	kubecrossImg := fmt.Sprintf("k8s.gcr.io/build-image/kube-cross:%s", kubecrossVer)

pkg/gcp/gcb/gcb.go

@@ -33,6 +33,7 @@ import (
 	"k8s.io/release/pkg/gcp/auth"
 	"k8s.io/release/pkg/gcp/build"
 	"k8s.io/release/pkg/git"
+	"k8s.io/release/pkg/kubecross"
 	"k8s.io/release/pkg/release"
 	"sigs.k8s.io/release-utils/util"
 )
@@ -350,16 +351,21 @@ func (g *GCB) SetGCBSubstitutions(toolOrg, toolRepo, toolRef string) (map[string
 
 	gcbSubs["BUILDVERSION"] = buildVersion
 
-	kubecrossBranches := []string{
-		g.options.Branch,
-		git.DefaultBranch,
+	kc := kubecross.New()
+	kcVersionBranch, err := kc.ForBranch(g.options.Branch)
+	if err != nil {
+		return gcbSubs, errors.Wrap(err, "retrieve kube-cross version")
 	}
+	gcbSubs["KUBE_CROSS_VERSION"] = kcVersionBranch
 
-	kubecrossVersion, kubecrossVersionErr := release.GetKubecrossVersion(kubecrossBranches...)
-	if kubecrossVersionErr != nil {
-		return gcbSubs, kubecrossVersionErr
+	kcVersionLatest := kcVersionBranch
+	if g.options.Branch != git.DefaultBranch {
+		kcVersionLatest, err = kc.Latest()
+		if err != nil {
+			return gcbSubs, errors.Wrap(err, "retrieve latest kube-cross version")
+		}
 	}
-	gcbSubs["KUBE_CROSS_VERSION"] = kubecrossVersion
+	gcbSubs["KUBE_CROSS_VERSION_LATEST"] = kcVersionLatest
 
 	buildVersionSemver, err := util.TagStringToSemver(buildVersion)
 	if err != nil {

pkg/gcp/gcb/gcb_test.go

@@ -19,6 +19,7 @@ package gcb_test
 import (
 	"errors"
 	"fmt"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -530,7 +531,7 @@ func dropDynamicSubstitutions(orig map[string]string) (result map[string]string)
 	result = orig
 
 	for k := range result {
-		if k == "BUILDVERSION" || k == "GCP_USER_TAG" || k == "KUBE_CROSS_VERSION" {
+		if k == "BUILDVERSION" || k == "GCP_USER_TAG" || strings.HasPrefix(k, "KUBE_CROSS_VERSION") {
 			delete(result, k)
 		}
 	}

pkg/kubecross/impl.go

@@ -0,0 +1,31 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package kubecross
+
+import "sigs.k8s.io/release-utils/http"
+
+//go:generate go run github.com/maxbrunsfeld/counterfeiter/v6 -generate
+//counterfeiter:generate . impl
+type impl interface {
+	GetURLResponse(url string, trim bool) (string, error)
+}
+
+type defaultImpl struct{}
+
+func (*defaultImpl) GetURLResponse(url string, trim bool) (string, error) {
+	return http.GetURLResponse(url, trim)
+}

pkg/kubecross/kubecross.go

@@ -0,0 +1,60 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package kubecross
+
+import (
+	"fmt"
+
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+
+	"k8s.io/release/pkg/git"
+)
+
+// KubeCross is the main structure of this package.
+type KubeCross struct {
+	impl impl
+}
+
+// New creates a new KubeCross instance.
+func New() *KubeCross {
+	return &KubeCross{&defaultImpl{}}
+}
+
+// Latest returns the latest available kubecross version.
+func (k *KubeCross) Latest() (string, error) {
+	return k.ForBranch(git.DefaultBranch)
+}
+
+// ForBranch returns the kubecross version for the provided branch.
+func (k *KubeCross) ForBranch(branch string) (string, error) {
+	logrus.Infof("Trying to retrieve kube-cross version for branch %s", branch)
+
+	const (
+		baseURL     = "https://raw.githubusercontent.com/kubernetes/kubernetes"
+		versionPath = "build/build-image/cross/VERSION"
+	)
+
+	url := fmt.Sprintf("%s/%s/%s", baseURL, branch, versionPath)
+	version, err := k.impl.GetURLResponse(url, true)
+	if err != nil {
+		return "", errors.Wrap(err, "get URL response")
+	}
+
+	logrus.Infof("Retrieved kube-cross version: %s", version)
+	return version, nil
+}

pkg/kubecross/kubecross_test.go

@@ -0,0 +1,96 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package kubecross
+
+import (
+	"testing"
+
+	"github.com/pkg/errors"
+	"github.com/stretchr/testify/require"
+
+	"k8s.io/release/pkg/kubecross/kubecrossfakes"
+)
+
+func TestLatest(t *testing.T) {
+	for _, tc := range []struct {
+		prepare func(*kubecrossfakes.FakeImpl)
+		expect  func(res string, err error)
+	}{
+		{ // success
+			prepare: func(mock *kubecrossfakes.FakeImpl) {
+				mock.GetURLResponseReturns("test", nil)
+			},
+			expect: func(res string, err error) {
+				require.Nil(t, err)
+				require.Equal(t, "test", res)
+			},
+		},
+		{ // failure GetURLResponse
+			prepare: func(mock *kubecrossfakes.FakeImpl) {
+				mock.GetURLResponseReturns("", errors.New(""))
+			},
+			expect: func(res string, err error) {
+				require.NotNil(t, err)
+				require.Empty(t, res)
+			},
+		},
+	} {
+		mock := &kubecrossfakes.FakeImpl{}
+		tc.prepare(mock)
+
+		kc := New()
+		kc.impl = mock
+
+		res, err := kc.Latest()
+		tc.expect(res, err)
+	}
+}
+
+func TestForBranch(t *testing.T) {
+	for _, tc := range []struct {
+		prepare func(*kubecrossfakes.FakeImpl)
+		expect  func(res string, err error)
+	}{
+		{ // success
+			prepare: func(mock *kubecrossfakes.FakeImpl) {
+				mock.GetURLResponseReturns("test", nil)
+			},
+			expect: func(res string, err error) {
+				require.Nil(t, err)
+				require.Equal(t, "test", res)
+			},
+		},
+		{ // failure GetURLResponse
+			prepare: func(mock *kubecrossfakes.FakeImpl) {
+				mock.GetURLResponseReturns("", errors.New(""))
+			},
+			expect: func(res string, err error) {
+				require.NotNil(t, err)
+				require.Empty(t, res)
+			},
+		},
+	} {
+		mock := &kubecrossfakes.FakeImpl{}
+		tc.prepare(mock)
+
+		kc := New()
+		kc.impl = mock
+
+		res, err := kc.ForBranch("")
+		tc.expect(res, err)
+	}
+}