Add publish action

Author: mrjvs

.github/workflows/publish.yml

@@ -0,0 +1,63 @@
+name: Build and Publish Docker Image
+
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: discourse
+  RELEASE_BRANCH: refs/heads/master
+  SHOULD_PUSH_IMAGE: ${{ (github.event_name == 'push' && (github.ref == 'refs/heads/master' || github.ref == 'refs/heads/dev')) || github.event_name == 'workflow_dispatch' }}
+
+jobs:
+  build-publish-amd64:
+    name: Build and Publish Docker Image (amd64)
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v5
+
+      - name: Set up QEMU for Docker
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log into the container registry
+        if: ${{ env.SHOULD_PUSH_IMAGE == 'true' }}
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract Docker metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=raw,value=latest,enable=${{ github.ref == env.RELEASE_BRANCH }}
+            type=raw,value=edge,enable=${{ github.ref == 'refs/heads/dev' }}
+            type=sha
+
+      - name: Prepare discourse dependencies
+        run: ./build.sh
+
+      - name: Build and push Docker image
+        id: build-and-push
+        uses: docker/build-push-action@v6
+        with:
+          platforms: linux/amd64
+          push: ${{ env.SHOULD_PUSH_IMAGE }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max