ci(agent-helper): version image independently of app release

.github/workflows/publish-agent-helper.yml

@@ -1,12 +1,16 @@
 name: Publish Agent Helper Image
 
 on:
-  release:
-    types: [published]
+  push:
+    branches: [main]
+    paths:
+      - images/agent-helper/**
+      - hack/agent_helper_image/**
+      - .github/workflows/publish-agent-helper.yml
   workflow_dispatch:
     inputs:
       tag:
-        description: optional version override (defaults to the latest git tag)
+        description: optional version override (defaults to images/agent-helper/VERSION)
         required: false
         type: string
   pull_request:
@@ -26,8 +30,6 @@ jobs:
       contents: read
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
-        with:
-          fetch-depth: 0
 
       - uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e # v7
         with:
@@ -38,24 +40,17 @@ jobs:
           version: 0.16.0
 
       - name: cross-compile helper binaries
-        run: go run ./hack/agent_helper_image
+        run: go run ./hack/agent_helper_image build
 
       - name: resolve version
         id: version
-        run: |
-          set -euo pipefail
-          if [ -n "${{ inputs.tag }}" ]; then
-            version="${{ inputs.tag }}"
-          elif [ "${{ github.event_name }}" = "release" ]; then
-            version="${{ github.ref_name }}"
-          else
-            version="$(git describe --tags --abbrev=0)"
-          fi
-          echo "value=$version" >> "$GITHUB_OUTPUT"
+        env:
+          INPUT_TAG: ${{ inputs.tag }}
+        run: go run ./hack/agent_helper_image version -tag "$INPUT_TAG"
 
       - uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
 
-      # Publish only on release / manual dispatch; pull_request runs build-only.
+      # Publish on push to main / manual dispatch; pull_request runs build-only.
       - name: generate GitHub App token
         id: app-token
         if: ${{ github.event_name != 'pull_request' }}
@@ -72,21 +67,29 @@ jobs:
           username: ${{ steps.app-token.outputs.app-slug }}
           password: ${{ steps.app-token.outputs.token }}
 
+      - name: check tag exists
+        id: exists
+        if: ${{ github.event_name != 'pull_request' }}
+        env:
+          IMAGE: ${{ env.IMAGE }}
+          VERSION: ${{ steps.version.outputs.value }}
+        run: go run ./hack/agent_helper_image exists -image "$IMAGE" -tag "$VERSION"
+
       - name: docker metadata
         id: meta
         uses: docker/metadata-action@dc802804100637a589fabce1cb79ff13a1411302 # v6.2.0
         with:
           images: ${{ env.IMAGE }}
           tags: |
             type=raw,value=${{ steps.version.outputs.value }}
-            type=raw,value=latest,enable=${{ github.event_name == 'release' && !github.event.release.prerelease }}
+            type=raw,value=latest,enable=${{ github.event_name != 'pull_request' }}
 
       - name: build and push
         uses: docker/build-push-action@53b7df96c91f9c12dcc8a07bcb9ccacbed38856a # v7.3.0
         with:
           context: images/agent-helper
           file: images/agent-helper/Dockerfile
           platforms: linux/amd64,linux/arm64
-          push: ${{ github.event_name != 'pull_request' }}
+          push: ${{ github.event_name != 'pull_request' && steps.exists.outputs.value != 'true' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}

hack/agent_helper_image/main.go

@@ -4,11 +4,14 @@
 package main
 
 import (
+	"bytes"
 	"flag"
 	"fmt"
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strconv"
+	"strings"
 )
 
 type target struct {
@@ -22,16 +25,39 @@ var targets = []target{
 }
 
 func main() {
-	dir := flag.String("dir", "images/agent-helper", "agent-helper image directory")
-	flag.Parse()
+	args := os.Args[1:]
+	cmd := "build"
+	if len(args) > 0 && !strings.HasPrefix(args[0], "-") {
+		cmd, args = args[0], args[1:]
+	}
 
-	if err := run(*dir); err != nil {
+	var err error
+	switch cmd {
+	case "build":
+		err = runBuild(args)
+	case "version":
+		err = runVersion(args)
+	case "exists":
+		err = runExists(args)
+	default:
+		err = fmt.Errorf("unknown command %q", cmd)
+	}
+	if err != nil {
 		fmt.Fprintln(os.Stderr, "agent_helper_image:", err)
 		os.Exit(1)
 	}
 }
 
-func run(dir string) error {
+func runBuild(args []string) error {
+	fs := flag.NewFlagSet("build", flag.ExitOnError)
+	dir := fs.String("dir", "images/agent-helper", "agent-helper image directory")
+	if err := fs.Parse(args); err != nil {
+		return err
+	}
+	return build(*dir)
+}
+
+func build(dir string) error {
 	distDir := filepath.Join(dir, "dist")
 	if err := os.MkdirAll(distDir, 0o755); err != nil {
 		return err
@@ -57,3 +83,100 @@ func run(dir string) error {
 	}
 	return nil
 }
+
+func runVersion(args []string) error {
+	fs := flag.NewFlagSet("version", flag.ExitOnError)
+	dir := fs.String("dir", "images/agent-helper", "agent-helper image directory")
+	tag := fs.String("tag", "", "explicit version override")
+	if err := fs.Parse(args); err != nil {
+		return err
+	}
+
+	version := strings.TrimSpace(*tag)
+	if version == "" {
+		data, err := os.ReadFile(filepath.Join(*dir, "VERSION"))
+		if err != nil {
+			return err
+		}
+		version = strings.TrimSpace(string(data))
+	}
+	if version == "" {
+		return fmt.Errorf("agent-helper version is empty")
+	}
+
+	fmt.Println(version)
+	return writeOutput("value", version)
+}
+
+func runExists(args []string) error {
+	fs := flag.NewFlagSet("exists", flag.ExitOnError)
+	image := fs.String("image", "", "image repository (without tag)")
+	tag := fs.String("tag", "", "image tag to check")
+	if err := fs.Parse(args); err != nil {
+		return err
+	}
+	if *image == "" || *tag == "" {
+		return fmt.Errorf("both -image and -tag are required")
+	}
+
+	ref := *image + ":" + *tag
+	exists, err := manifestExists(ref)
+	if err != nil {
+		return err
+	}
+	if exists {
+		fmt.Printf("::notice::%s already exists; skipping push\n", ref)
+	}
+	return writeOutput("value", strconv.FormatBool(exists))
+}
+
+func manifestExists(ref string) (bool, error) {
+	var stderr bytes.Buffer
+	cmd := exec.Command("docker", "manifest", "inspect", ref)
+	cmd.Stderr = &stderr
+	if err := cmd.Run(); err != nil {
+		msg := strings.TrimSpace(stderr.String())
+		if isAbsent(msg) {
+			return false, nil
+		}
+		return false, fmt.Errorf(
+			"docker manifest inspect %s: %w: %s", ref, err, msg,
+		)
+	}
+	return true, nil
+}
+
+func isAbsent(stderr string) bool {
+	s := strings.ToLower(stderr)
+	for _, marker := range []string{
+		"no such manifest",
+		"manifest unknown",
+		"name unknown",
+		"not found",
+		"denied",
+		"unauthorized",
+		"forbidden",
+	} {
+		if strings.Contains(s, marker) {
+			return true
+		}
+	}
+	return false
+}
+
+func writeOutput(key, value string) error {
+	out := os.Getenv("GITHUB_OUTPUT")
+	if out == "" {
+		return nil
+	}
+	f, err := os.OpenFile(out, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o644)
+	if err != nil {
+		return err
+	}
+	_, writeErr := fmt.Fprintf(f, "%s=%s\n", key, value)
+	closeErr := f.Close()
+	if writeErr != nil {
+		return writeErr
+	}
+	return closeErr
+}

images/agent-helper/VERSION

@@ -0,0 +1 @@
+0.1.0