add line changes diff bot to CI (#1863)

.github/workflows/szdiff.yml

@@ -0,0 +1,51 @@
+name: Check Line Counts
+on:
+  pull_request:
+
+# Cancel the workflow in progress in newer build is about to start.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  szdiff:
+    name: Core Library Line Difference
+    permissions:
+      contents: read
+      pull-requests: write
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code from pr
+        uses: actions/checkout@v2
+        with:
+          ref: ${{ github.event.pull_request.head.ref }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+          path: pr
+      - name: Checkout code from base
+        uses: actions/checkout@v2
+        with:
+          ref: ${{ github.event.pull_request.base.sha }}
+          path: base
+      - name: Set up Python 3.10
+        uses: actions/setup-python@v4
+        with:
+          python-version: '3.10'
+      - name: Count Lines Of Code
+        run: |
+          pip install tabulate
+          BASE="$GITHUB_WORKSPACE/base"
+          PR="$GITHUB_WORKSPACE/pr"
+          cp "$PR/sz.py" .
+          echo "loc_content<<EOF" >> "$GITHUB_ENV"
+          python sz.py "$BASE" "$PR" >> "$GITHUB_ENV"
+          echo "EOF" >> "$GITHUB_ENV"
+      - name: Comment Code Lines
+        continue-on-error: false
+        uses: marocchino/sticky-pull-request-comment@v2
+        with:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          header: LOC
+          ignore_empty: true
+          skip_unchanged: true
+          recreate: true
+          message: ${{ env.loc_content }}