github: check new kernel

.github/workflows/cron.yml

@@ -0,0 +1,35 @@
+name: Auto-update firmware
+
+on:
+  push:
+    branches:
+      - main
+  schedule:
+    # daily, hour and minute chosen arbitrarily
+    - cron: "32 14 * * *"
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: true
+
+      - name: Set up Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.18
+
+      - 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)"
+
+      - name: Fetch latest kernel
+        if: steps.check.outputs.version != ''
+        run: echo "checkout ${{steps.check.outputs.version}}"
+
+      - name: Commit the new kernel
+        uses: stefanzweifel/git-auto-commit-action@v4
+        with:
+          commit_message: kernel ${{steps.check.outputs.version}}

cmd/check-update/main.go

@@ -0,0 +1,104 @@
+package main
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+func main() {
+	if err := run(); err != nil {
+		log.Println(err)
+
+		os.Exit(1)
+	}
+}
+
+const baseURL = "https://archive.raspberrypi.org/debian/"
+const packagesURL = baseURL + "dists/buster/main/binary-armhf/Packages"
+
+func run() error {
+	log.Println("checking:", packagesURL)
+	kernelPrefix := "Filename: pool/main/r/raspberrypi-firmware/raspberrypi-kernel_"
+	version := ""
+	versionPrefix := "Version: "
+	err := scanOnlineTextFile(packagesURL, func(s string) bool {
+		if strings.HasPrefix(s, versionPrefix) {
+			version = s[len(versionPrefix):]
+		}
+		if strings.HasPrefix(s, kernelPrefix) {
+			return true
+		}
+		return false
+	})
+	if version == "" {
+		if err != nil {
+			return err
+		}
+		return errors.New("could not find kernel version in package list")
+	}
+
+	before, after, found := strings.Cut(version, ":")
+	if !found {
+		after = before
+	}
+	tagName, _, _ := strings.Cut(after, "~")
+
+	log.Println("latest version:", tagName)
+
+	tags, err := gitTags("linux-sources")
+	if err != nil {
+		return err
+	}
+	for _, tag := range tags {
+		if tagName == tag {
+			log.Println("already up to date")
+			return nil
+		}
+	}
+	log.Println("outdated tag", tags)
+	fmt.Println(tagName)
+
+	return nil
+}
+
+func gitTags(folder string) ([]string, error) {
+	current, err := os.Getwd()
+	if err != nil {
+		return nil, err
+	}
+	defer os.Chdir(current)
+
+	err = os.Chdir(folder)
+	if err != nil {
+		return nil, err
+	}
+	cmd := exec.Command("git", "tag", "--points-at", "HEAD")
+	cmd.Stderr = os.Stderr
+	out, err := cmd.Output()
+	if err != nil {
+		return nil, err
+	}
+	return strings.Split(strings.TrimSpace(string(out)), "\n"), nil
+}
+
+func scanOnlineTextFile(url string, stopScanning func(string) bool) error {
+	resp, err := http.Get(url)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	scanner := bufio.NewScanner(resp.Body)
+	for scanner.Scan() {
+		if stopScanning(scanner.Text()) {
+			break
+		}
+	}
+	return scanner.Err()
+}