ci: add lint and syntax check workflow

.gitea/workflows/ci.yml

@@ -0,0 +1,37 @@
+name: CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  lint:
+    name: Lint & Check
+    runs-on: ubuntu-latest
+    container:
+      image: python:3.11-slim
+
+    steps:
+      - name: Setup and checkout
+        run: |
+          apt-get update -qq && apt-get install -yqq --no-install-recommends git >/dev/null
+          git clone --depth 1 --branch "${GITHUB_REF_NAME}" \
+            "https://oauth2:${{ github.token }}@${GITHUB_SERVER_URL#https://}/${GITHUB_REPOSITORY}.git" .
+
+      - name: Install tools
+        run: pip install -q ruff
+
+      - name: Syntax check
+        run: python -m py_compile gitea-ci.py
+
+      - name: Lint
+        run: ruff check gitea-ci.py
+
+      - name: Test --help
+        run: python gitea-ci.py --help