action check diffs (#40)

.github/workflows/check-diff.yml

@@ -0,0 +1,26 @@
+name: Check GraphQL Diff
+
+on:
+  pull_request:
+
+jobs:
+  check-diff:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-20.04]
+        go-version:
+          - 1.20.6
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v3
+
+    - name: Set up Go ${{ matrix.go-version}}
+      uses: actions/setup-go@v3
+      with:
+        go-version: ${{ matrix.go-version}}
+
+    - name: Run make check-diff
+      run: |
+        make check-diff

Makefile

@@ -1,8 +1,8 @@
 SHELL = /bin/bash
 
-.PHONY: all build test
+.PHONY: all build test check-diff
 
-all: build test
+all: build test check-diff
 
 build:
 	go build
@@ -14,3 +14,11 @@ test: build
 		echo "Merging $$dir into $$output..."; \
 		./gqlmerge $$dir $$output; \
 	done
+
+check-diff: build test
+	@if git diff --exit-code --quiet -- '*.graphql'; then \
+		echo "Ok"; \
+	else \
+		echo "Error: Differences found in generated.graphql files"; \
+		exit -1; \
+	fi