Add a release workflow that pushes the container image on a new tag

Also lets CI fetch Reef from this server, as the other sharks repositories do.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -8,6 +8,8 @@ on:
 jobs:
   test:
     runs-on: ubuntu-latest
+    env:
+      GOPRIVATE: git.veillax.com
     steps:
       - uses: actions/checkout@v4
 
@@ -15,6 +17,11 @@ jobs:
         with:
           go-version-file: go.mod
 
+      # Go fetches Reef straight from this server. Harmless for public repositories and
+      # what makes private ones work.
+      - name: Let Go fetch modules from this server
+        run: git config --global url."https://x-access-token:${{ secrets.GITHUB_TOKEN }}@git.veillax.com/".insteadOf "https://git.veillax.com/"
+
       - name: Formatting
         run: |
           unformatted=$(gofmt -l cmd internal)

.gitea/workflows/release.yml

@@ -0,0 +1,59 @@
+name: Release
+
+# Push a tag such as v0.1.0 to build and publish the container image:
+#   git tag -a v0.1.0 -m "sandbar v0.1.0" && git push origin v0.1.0
+on:
+  push:
+    tags: ['v*']
+
+jobs:
+  image:
+    runs-on: ubuntu-latest
+    env:
+      GOPRIVATE: git.veillax.com
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+
+      # Go fetches Reef straight from this server. Harmless for public repositories and
+      # what makes private ones work.
+      - name: Let Go fetch modules from this server
+        run: git config --global url."https://x-access-token:${{ secrets.GITHUB_TOKEN }}@git.veillax.com/".insteadOf "https://git.veillax.com/"
+
+      - name: Test
+        run: |
+          go vet ./...
+          go test ./...
+
+      # The Dockerfile packages these binaries, so the arm64 image needs no emulation.
+      - name: Build the binaries
+        run: |
+          for a in amd64 arm64; do
+            mkdir -p dist/bin/linux_$a
+            CGO_ENABLED=0 GOOS=linux GOARCH=$a go build -trimpath \
+              -ldflags "-s -w -X main.version=${GITHUB_REF_NAME}" \
+              -o dist/bin/linux_$a/sandbar ./cmd/sandbar
+          done
+
+      # Optional secret REGISTRY_TOKEN (and variable REGISTRY_USER): an access token with
+      # package write permission, for servers where the job token can't push.
+      - name: Build and push the container image
+        env:
+          REGISTRY_TOKEN: ${{ secrets.REGISTRY_TOKEN || secrets.GITHUB_TOKEN }}
+          REGISTRY_USER: ${{ vars.REGISTRY_USER || github.actor }}
+        run: |
+          host=${GITHUB_SERVER_URL#*://}
+          owner=$(echo "$GITHUB_REPOSITORY_OWNER" | tr 'A-Z' 'a-z')
+          image="$host/$owner/sandbar"
+          echo "$REGISTRY_TOKEN" | docker login "$host" -u "$REGISTRY_USER" --password-stdin
+          # a container-driver builder can build several architectures in one go
+          docker buildx create --name release --driver docker-container --use >/dev/null 2>&1 || docker buildx use release
+          tags="-t $image:$GITHUB_REF_NAME"
+          case "$GITHUB_REF_NAME" in
+            *-*) ;;                       # pre-releases (v1.0.0-rc1) don't move :latest
+            *) tags="$tags -t $image:latest" ;;
+          esac
+          docker buildx build --platform linux/amd64,linux/arm64 $tags --push .