create update-preload-version script

Makefile

@@ -986,6 +986,10 @@ update-golint-version:
 	(cd hack/update/golint_version && \
 	 go run update_golint_version.go)
 
+.PHONY: update-preload-version
+update-preload-version:
+	(cd hack/update/preload_version && \
+	 go run update_preload_version.go)
 
 .PHONY: update-kubernetes-version-pr
 update-kubernetes-version-pr:

hack/update/preload_version/update_preload_version.go

@@ -0,0 +1,114 @@
+/*
+Copyright 2021 The Kubernetes Authors All rights reserved.
+
+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.
+*/
+
+/*
+Script expects the following env variables:
+ - UPDATE_TARGET=<string>: optional - if unset/absent, default option is "fs"; valid options are:
+   - "fs"  - update only local filesystem repo files [default]
+   - "gh"  - update only remote GitHub repo files and create PR (if one does not exist already)
+   - "all" - update local and remote repo files and create PR (if one does not exist already)
+ - GITHUB_TOKEN=<string>: GitHub [personal] access token
+   - note: GITHUB_TOKEN is required if UPDATE_TARGET is "gh" or "all"
+*/
+
+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"time"
+
+	"k8s.io/klog/v2"
+	"k8s.io/minikube/hack/update"
+)
+
+const (
+	preloadFile      = "pkg/minikube/download/preload.go"
+	preloadVersionRE = `v[0-9]*`
+)
+
+var (
+	schema = map[string]update.Item{
+		preloadFile: {
+			Replace: map[string]string{
+				`PreloadVersion = "v[0-9]*"`: `PreloadVersion = "v{{.UpdateVersion}}"`,
+			},
+		},
+	}
+
+	// prBranchPrefix is the PR branch prefix; will be appended with the first 7 characters of the PR commit SHA.
+	prBranchPrefix = "update-preload-version_"
+	prTitle        = `update preload version: {stable: "{{.StableVersion}}"}`
+)
+
+// Data holds updated preload version.
+type Data struct {
+	UpdateVersion string `json:"stableVersion"`
+}
+
+func main() {
+	const cxTimeout = 300 * time.Second
+	ctx, cancel := context.WithTimeout(context.Background(), cxTimeout)
+	defer cancel()
+
+	// Get current preload version.
+	vCurrent, err := getPreloadVersion()
+	if err != nil {
+		klog.Fatalf("failed to get current preload version: %v", err)
+	}
+	if vCurrent == 0 {
+		klog.Fatalf("cannot determine current preload version")
+	}
+	klog.Infof("current preload version: %d", vCurrent)
+
+	// Update preload version.
+	updatedVersion := vCurrent + 1
+
+	data := Data{UpdateVersion: fmt.Sprint(updatedVersion)}
+	klog.Infof("updated preload version: %s", data.UpdateVersion)
+
+	update.Apply(ctx, schema, data, prBranchPrefix, prTitle, -1)
+}
+
+// getPreloadVersion returns current preload version and any error.
+func getPreloadVersion() (int, error) {
+	blob, err := os.ReadFile(filepath.Join(update.FSRoot, preloadFile))
+	if err != nil {
+		return 0, err
+	}
+	// Match PreloadVersion.
+	re := regexp.MustCompile(fmt.Sprintf(`PreloadVersion = "%s"`, preloadVersionRE))
+	version := re.FindSubmatch(blob)
+	if version == nil {
+		return 0, nil
+	}
+	// Match version within PreloadVersion.
+	re = regexp.MustCompile(preloadVersionRE)
+	version = re.FindSubmatch(version[0])
+	if version == nil {
+		return 0, nil
+	}
+	// Convert to integer, drop 'v'.
+	current, err := strconv.Atoi(string(version[0])[1:])
+	if err != nil {
+		return 0, err
+	}
+	return current, nil
+}