Open pull request automatically when line-openapi is updated

.github/workflows/diff-check.yml

@@ -0,0 +1,45 @@
+name: Diff check and open pull request
+
+on:
+  push:
+    branches:
+      - 'master'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Setup
+        uses: actions/checkout@v3
+        with:
+          submodules: recursive
+      - name: Set up Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.x'
+      - name: Generate codes
+        run: python generate-code.py
+      - name: Install bump
+        run: pip install bump
+      - name: Mark if diff exists
+        run: |
+          diff=$(git --no-pager diff --name-only)
+          echo "DIFF_IS_EMPTY=$([[ -z "$diff" ]] && echo 'true' || echo 'false')" >> $GITHUB_ENV
+          echo "CURRENT_DATETIME=$(date +'%Y%m%d%H%M%S')" >> $GITHUB_ENV
+
+      ## TODO: Enable merge change into master directly
+      - name: Open pull request if generated code is not same as current one
+        if: ${{ env.DIFF_IS_EMPTY != 'true' }}
+        run: |
+          git config user.name github-actions
+          git config user.email github-actions@github.com
+          git checkout -b update-diff-${{ env.CURRENT_DATETIME }}
+          bump -m -r linebot/__about__.py
+          python generate-code.py
+          git add .
+          git commit -m "Codes are generated by openapi"
+          git push origin update-diff-${{ env.CURRENT_DATETIME }}
+          gh pr create -B ${{ github.ref_name }} -t "Codes are generated by openapi" -b ""
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}