Add GHCR Docker publish workflow

Author: vdw

.github/workflows/docker-publish.yml

@@ -0,0 +1,59 @@
+name: Publish Docker image
+
+on:
+  push:
+    branches:
+      - main
+    tags:
+      - "v*"
+  workflow_dispatch:
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract image metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=ref,event=tag
+            type=sha
+            type=raw,value=latest,enable={{is_default_branch}}
+
+      - name: Build and push image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          platforms: linux/amd64,linux/arm64
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max

README.md

@@ -122,3 +122,24 @@ The compose service includes Docker log rotation using:
 
 - `max-size: 10m`
 - `max-file: 3`
+
+## Prebuilt Image (GHCR)
+
+This repository includes a GitHub Actions workflow at `.github/workflows/docker-publish.yml`.
+
+- On each push to `main`, it builds and publishes a multi-arch image to GHCR.
+- On tags like `v1.0.0`, it also publishes tag-based versions.
+- You can also run it manually from the Actions tab (`workflow_dispatch`).
+
+Published image name:
+
+```text
+ghcr.io/vdw/hetzner_ddns
+```
+
+Run prebuilt image on a server:
+
+```bash
+docker pull ghcr.io/vdw/hetzner_ddns:latest
+docker run -d --name hetzner-ddns --restart unless-stopped --env-file .env ghcr.io/vdw/hetzner_ddns:latest
+```