add black ci (#189)

.github/workflows/test.yml

@@ -39,3 +39,32 @@ jobs:
       - name: Run tests
         run: |
           pytest 
+
+  black:
+    strategy:
+      matrix:
+        version: [3.11]
+        os: [ubuntu-latest]
+    runs-on: ${{matrix.os}}
+    steps:
+      - name: Checking out repository
+        uses: actions/checkout@8f4b7f84864484a7bf31766abe9204da3cbe65b3 # v3.5.0
+      - name: Setting up python
+        uses: actions/setup-python@d27e3f3d7c64b4bbf8e4abfb9b63b83e846e0435 # v4.5.0
+      - name: Fetching Base Branch
+        # We have to explicitly fetch the base branch as well
+        run: git fetch --no-tags --prune --depth=1 origin "${GITHUB_BASE_REF?}:${GITHUB_BASE_REF?}"
+      - name: Install black
+        run: |
+          python3 -m pip install black==23.3
+      - name: Check if modified files are formatted
+        run: |
+          # The filter lowercase `d` means to exclude deleted files.
+          git diff "${GITHUB_BASE_REF?}" --name-only --diff-filter=d \
+            -- '*.py' \
+            | xargs --no-run-if-empty black --check --diff --verbose
+      - name: Instructions for fixing the above linting errors
+        if: failure()
+        run: |
+          printf "You can fix formatting by running 'black' on the modified python files:\n"
+          printf "  git diff ${GITHUB_BASE_REF?} --name-only -- '*.py' ':!third_party' | xargs black\n"