ci: add protobuf compat tests for both DGraph Latest and HEAD

Split protobuf compatibility testing into two jobs:
- test-pydgraph-protobuf-compat-dgraph-latest: Tests against released DGraph
- test-pydgraph-protobuf-compat-dgraph-head: Tests against DGraph HEAD

This mirrors the structure of the main test matrix.

Author: mlwelles

.github/workflows/ci-pydgraph-tests.yml

@@ -85,8 +85,10 @@ jobs:
       - name: Run tests
         working-directory: ./pydgraph
         run: DGRAPH_IMAGE_TAG=local make test
-  test-pydgraph-protobuf-compat:
-    name: Test Pydgraph (Python ${{ matrix.python-version }} / ${{ matrix.protobuf-version }})
+  test-pydgraph-protobuf-compat-dgraph-latest:
+    name:
+      Test Pydgraph (Python ${{ matrix.python-version }} / ${{ matrix.protobuf-version }} / DGraph
+      Latest)
     runs-on: ubuntu-latest
     strategy:
       matrix:
@@ -114,3 +116,56 @@ jobs:
         run: uv pip install "${{ matrix.protobuf-version }}"
       - name: Run tests
         run: make test
+  test-pydgraph-protobuf-compat-dgraph-head:
+    name:
+      Test Pydgraph (Python ${{ matrix.python-version }} / ${{ matrix.protobuf-version }} / DGraph
+      HEAD)
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.9", "3.14"]
+        protobuf-version:
+          - protobuf>=4.23.0,<5.0.0
+          - protobuf>=5.0.0,<6.0.0
+    steps:
+      - name: Checkout Dgraph main latest
+        uses: actions/checkout@v5
+        with:
+          path: dgraph
+          repository: dgraph-io/dgraph
+          ref: main
+      - name: Setup Go
+        uses: actions/setup-go@v6
+        with:
+          go-version-file: dgraph/go.mod
+      - name: Build dgraph binary
+        working-directory: ./dgraph
+        run: make docker-image
+      - name: Install dgraph binary
+        working-directory: ./dgraph
+        run: mv dgraph/dgraph ~/go/bin/dgraph
+      - name: Checkout pydgraph
+        uses: actions/checkout@v5
+        with:
+          path: pydgraph
+          repository: dgraph-io/pydgraph
+          ref: ${{ github.ref }}
+      - name: Setup python runtime and tooling
+        uses: ./pydgraph/.github/actions/setup-python-and-tooling
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Pin python version
+        working-directory: ./pydgraph
+        run: uv python pin ${{ matrix.python-version }}
+      - name: Setup project dependencies
+        working-directory: ./pydgraph
+        run: INSTALL_MISSING_TOOLS=true make setup
+      - name: Sync python virtualenv
+        working-directory: ./pydgraph
+        run: make sync
+      - name: Install specific protobuf version
+        working-directory: ./pydgraph
+        run: uv pip install "${{ matrix.protobuf-version }}"
+      - name: Run tests
+        working-directory: ./pydgraph
+        run: DGRAPH_IMAGE_TAG=local make test