Fix grid workflow to check if new solutions are added

Author: NinePiece2

.github/workflows/update-leetcode-grid.yml

@@ -1,10 +1,6 @@
 name: Update LeetCode Grid
 
 on:
-  # push:
-  #   paths:
-  #     - "Solutions/**"
-  #     - "Scripts/update_project_readme.py"
   workflow_dispatch:
   workflow_run:
     workflows: ["Sync Leetcode"]
@@ -14,41 +10,57 @@ on:
 jobs:
   update-readme:
     runs-on: ubuntu-latest
-    if: >
-      github.event.workflow_run.conclusion == 'success' &&
-      contains(github.event.workflow_run.head_commit.message, 'Solutions/')
+    if: github.event.workflow_run.conclusion == 'success'
 
     steps:
       - name: Checkout repository
         uses: actions/checkout@v5
+        with:
+          ref: ${{ github.event.workflow_run.head_branch }}
+
+      - name: Check for Solutions/ changes
+        id: changes
+        run: |
+          git fetch origin ${{ github.event.workflow_run.head_sha }}
+          git diff --name-only ${{ github.event.workflow_run.head_sha }}^ ${{ github.event.workflow_run.head_sha }} > files.txt
+          if grep -q '^Solutions/' files.txt; then
+            echo "changed=true" >> $GITHUB_OUTPUT
+          else
+            echo "changed=false" >> $GITHUB_OUTPUT
+          fi
 
       - name: Set up Python
+        if: steps.changes.outputs.changed == 'true'
         uses: actions/setup-python@v6
         with:
           python-version: "3.11"
 
       - name: Install dependencies
+        if: steps.changes.outputs.changed == 'true'
         run: |
           pip install pyyaml requests
 
       - name: Restore LeetCode API cache
+        if: steps.changes.outputs.changed == 'true'
         uses: actions/cache@v4
         with:
           path: .leetcode_cache.json
           key: leetcode-cache
 
       - name: Generate LeetCode README table
+        if: steps.changes.outputs.changed == 'true'
         run: |
-            python ./Scripts/update_project_readme.py
-      
+          python ./Scripts/update_project_readme.py
+
       - name: Save updated cache
-        if: always()
+        if: always() && steps.changes.outputs.changed == 'true'
         uses: actions/cache/save@v4
         with:
           path: .leetcode_cache.json
           key: leetcode-cache
 
       - name: Commit and push changes
+        if: steps.changes.outputs.changed == 'true'
         run: |
           git config --local user.name "github-actions[bot]"
           git config --local user.email "github-actions[bot]@users.noreply.github.com"
@@ -59,4 +71,4 @@ jobs:
           git fetch origin ${{ github.ref_name }}
           git rebase origin/${{ github.ref_name }}
 
-          git push origin HEAD:${{ github.ref_name }}
+          git push origin HEAD:${{ github.ref_name }}