CI: Update workflow.

.github/workflows/docker-image.yml

@@ -1,18 +1,51 @@
-name: Leekbot Docker image CI
+name: Build and publish the leekbot docker image.
 
 on:
   push:
-    branches: [ "main" ]
-  pull_request:
-    branches: [ "main" ]
+    branches: ['main']
 
-jobs:
-
-  build:
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: leekbot
 
+jobs:
+  build-and-push-leekbot:
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+      attestations: write
+      id-token: write
 
     steps:
-    - uses: actions/checkout@v4
-    - name: Build the Docker image
-      run: docker build . --file Dockerfile --tag leekbot:$(date +%s)
+      - name: Repository checkout
+        uses: actions/checkout@v4
+
+      - name: Container registry login
+        uses: docker/login-action@65b78e6e13532edd9afa3aa52ac7964289d1a9c1
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@9ec57ed1fcdbf14dcef7dfbe97b2010124a938b7
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+
+      - name: Build and push Leekbot
+        id: push
+        uses: docker/build-push-action@f2a1d5e99d037542a71f64918e516c093c6f3fc4
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+
+      - name: Generate artifact attestation
+        uses: actions/attest-build-provenance@v2
+        with:
+          subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME}}
+          subject-digest: ${{ steps.push.outputs.digest }}
+          push-to-registry: true