github: check new kernel commit

.github/workflows/cron.yml

@@ -1,4 +1,4 @@
-name: Auto-update firmware
+name: Auto-update kernel
 
 on:
   push:
@@ -13,8 +13,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
-        with:
-          submodules: true
 
       - name: Set up Go
         uses: actions/setup-go@v2
@@ -23,13 +21,13 @@ jobs:
 
       - name: Check latest kernel version from https://archive.raspberrypi.org/debian/
         id: check
-        run: echo "::set-output name=version::$(go run ./cmd/check-update/main.go)"
+        run: echo "::set-output name=sha::$(go run ./cmd/check-update/main.go)"
 
       - name: Fetch latest kernel
-        if: steps.check.outputs.version != ''
+        if: steps.check.outputs.sha != ''
-        run: echo "checkout ${{steps.check.outputs.version}}"
+        run: echo "checkout ${{steps.check.outputs.sha}}"
 
       - name: Commit the new kernel
         uses: stefanzweifel/git-auto-commit-action@v4
         with:
-          commit_message: kernel ${{steps.check.outputs.version}}
+          commit_message: kernel ${{steps.check.outputs.sha}}

cmd/check-update/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bufio"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"log"
@@ -51,40 +52,64 @@ func run() error {
 
 	log.Println("latest version:", tagName)
 
-	tags, err := gitTags("linux-sources")
+	latestSha, err := githubCommitSha(tagName)
 	if err != nil {
 		return err
 	}
-	for _, tag := range tags {
+	log.Println("latest commit:", latestSha)
-		if tagName == tag {
+
-			log.Println("already up to date")
+	currentSha, err := submoduleSha("linux-sources")
-			return nil
+	if err != nil {
-		}
+		return err
 	}
-	log.Println("outdated tag", tags)
+	log.Println("submodule commit:", currentSha)
-	fmt.Println(tagName)
+
+	if latestSha == currentSha {
+		log.Println("already up to date")
+		return nil
+	}
+	fmt.Println(latestSha)
 
 	return nil
 }
 
-func gitTags(folder string) ([]string, error) {
+func githubCommitSha(tagName string) (string, error) {
-	current, err := os.Getwd()
+	req, err := http.NewRequest("GET", "https://api.github.com/repos/raspberrypi/linux/git/ref/tags/"+tagName, nil)
 	if err != nil {
-		return nil, err
+		return "", err
 	}
-	defer os.Chdir(current)
+	req.Header.Add("Accept", "application/vnd.github.v3+json")
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return "", err
+	}
+	defer resp.Body.Close()
 
-	err = os.Chdir(folder)
+	type githubResponse struct {
-	if err != nil {
+		Message string `json:"message"`
-		return nil, err
+		Object  struct {
+			Sha string `json:"sha"`
+		} `json:"object"`
 	}
-	cmd := exec.Command("git", "tag", "--points-at", "HEAD")
+	var gr githubResponse
+	err = json.NewDecoder(resp.Body).Decode(&gr)
+	if err != nil {
+		return "", err
+	}
+	if gr.Object.Sha == "" {
+		return "", errors.New("could not get sha: " + gr.Message)
+	}
+	return gr.Object.Sha, nil
+}
+
+func submoduleSha(submodule string) (string, error) {
+	cmd := exec.Command("git", "rev-parse", "HEAD:"+submodule)
 	cmd.Stderr = os.Stderr
 	out, err := cmd.Output()
 	if err != nil {
-		return nil, err
+		return "", err
 	}
-	return strings.Split(strings.TrimSpace(string(out)), "\n"), nil
+	return strings.TrimSpace(string(out)), nil
 }
 
 func scanOnlineTextFile(url string, stopScanning func(string) bool) error {