[Chore] Build Docker Images on pushes to develop, main (#444)

Co-authored-by: Tim Lorsbach <tim@lorsba.ch>
Reviewed-on: enviPath/enviPy#444

.gitea/workflows/build-image.yaml

@@ -0,0 +1,64 @@
+name: Build Docker Image
+
+# Trigger manually or when a PR to main is completed.
+on:
+  workflow_dispatch:
+  pull_request:
+    branches:
+      - main
+      - develop
+    types:
+      - closed
+
+jobs:
+  build-and-push:
+    if: ${{ github.event_name == 'workflow_dispatch' || github.event.pull_request.merged == true }}
+    runs-on: ubuntu-latest
+    steps:
+      # Fetch the repository content for the Docker build context.
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      # Enable Buildx for BuildKit features (incl. SSH mount support).
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      # Authenticate against the container registry before pushing images.
+      - name: Log in to container registry
+        uses: docker/login-action@v3
+        with:
+          registry: git.envipath.com
+          username: ${{ secrets.CI_REGISTRY_USER }}
+          password: ${{ secrets.CI_REGISTRY_PASSWORD }}
+
+      # Generate image tags/labels:
+      # - main branch gets stable "envipy" and "latest" tags
+      # - every build gets an increasing build number tag
+      # - branch-prefixed commit SHA tag remains for traceability
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: git.envipath.com/envipath/envipy
+          tags: |
+            type=raw,value=envipy,enable=${{ github.ref_name == 'main' }}
+            type=raw,value=latest,enable=${{ github.ref_name == 'main' }}
+            type=raw,value=build-${{ github.run_number }}
+            type=sha,prefix={{branch}}-
+
+      # Load SSH key so Docker can pull private git+ssh dependencies during build.
+      - name: Setup SSH for private git dependencies
+        uses: webfactory/ssh-agent@v0.9.0
+        with:
+          ssh-private-key: ${{ secrets.ENVIPY_CI_PRIVATE_KEY }}
+
+      # Build and push the production image; forward SSH agent without registry cache reuse.
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: Dockerfile
+          push: true
+          ssh: default
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}