test deploy to dev with em_version

.docker/dockerfile

@@ -8,6 +8,7 @@ RUN go build -o emmer .
 
 # add (non-root) user, expose correct port
 FROM alpine:3.23
+ARG TAG
 RUN addgroup -S appgroup && adduser -S appuser -G appgroup
 COPY --from=builder /app/emmer /usr/local/bin/emmer
 RUN mkdir /data

.github/workflows/deploy_dev.yaml

@@ -0,0 +1,35 @@
+name: deploy
+
+on:
+  push:
+    branches: main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: checkout code
+        uses: actions/checkout@v4
+
+      - name: set up docker buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: log in to docker hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: extract tag name
+        id: tag
+        run: echo "TAG=${GITHUB_REF#refs/tags/}" >> $GITHUB_OUTPUT
+
+      - name: build and push
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: .docker/Dockerfile
+          push: true
+          tags: ${{ secrets.DOCKERHUB_USERNAME }}/emmer:dev
+          build-args: TAG=dev