Release from tag (#244)

Release a tagged docker image from git tag.

Can't really test without merging.

.github/workflows/release-from-tag.yml

@@ -0,0 +1,45 @@
+name: Release from tag
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  push_to_registry:
+    name: Push Docker Image to GitHub Packages
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    env:
+      DOCKER_METADATA_PR_HEAD_SHA: true
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Log in to the container registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/xmtp/xmtpd
+          tags: |
+            type=ref,event=tag
+            type=semver,pattern={{version}}
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v6
+        id: push
+        with:
+          context: .
+          file: ./dev/docker/Dockerfile
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          build-args: "GIT_COMMIT=${{ github.event_name != 'pull_request' && github.sha || github.event.pull_request.head.sha }}"