Update README with complete workflow example for PR comment trigger

Co-authored-by: mmcky <[email protected]>

Author: Copilot

.github/actions/code-style-checker/README.md

@@ -44,25 +44,144 @@ jobs:
     runs-on: ubuntu-latest
     
     steps:
+    - name: Get PR information
+      id: pr
+      uses: actions/github-script@v7
+      with:
+        script: |
+          const { data: pullRequest } = await github.rest.pulls.get({
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            pull_number: context.issue.number,
+          });
+          
+          core.setOutput('head-sha', pullRequest.head.sha);
+          core.setOutput('head-ref', pullRequest.head.ref);
+          core.setOutput('base-sha', pullRequest.base.sha);
+    
     - name: Checkout PR branch
       uses: actions/checkout@v4
       with:
         token: ${{ secrets.GITHUB_TOKEN }}
-        ref: ${{ github.event.pull_request.head.ref }}
+        ref: ${{ steps.pr.outputs.head-ref }}
+        fetch-depth: 0
     
     - name: Get changed files
       id: changed-files
       uses: tj-actions/changed-files@v40
       with:
         files: '**/*.md'
+        base_sha: ${{ steps.pr.outputs.base-sha }}
+        sha: ${{ steps.pr.outputs.head-sha }}
+    
+    - name: Check if any markdown files changed
+      id: check-files
+      run: |
+        if [ -z "${{ steps.changed-files.outputs.all_changed_files }}" ]; then
+          echo "no-files=true" >> $GITHUB_OUTPUT
+          echo "No markdown files were changed in this PR"
+        else
+          echo "no-files=false" >> $GITHUB_OUTPUT
+          echo "Changed markdown files:"
+          echo "${{ steps.changed-files.outputs.all_changed_files }}"
+        fi
     
-    - name: Format markdown files
+    - name: Format MyST markdown files
+      if: steps.check-files.outputs.no-files == 'false'
+      id: format
       uses: QuantEcon/meta/.github/actions/code-style-checker@main
       with:
         files: ${{ steps.changed-files.outputs.all_changed_files }}
+        check-myst-code-cells: 'true'
+        check-markdown-blocks: 'true'
+        python-languages: 'python,python3,ipython,ipython3'
+        black-args: '--line-length=88'
+        commit-files: 'true'
+        git-user-name: 'GitHub Action'
+        git-user-email: '[email protected]'
     
     - name: Push changes
-      run: git push
+      if: steps.check-files.outputs.no-files == 'false' && steps.format.outputs.changes-made == 'true'
+      run: |
+        git push
+        echo "Successfully pushed formatting changes"
+    
+    - name: Post comment with results
+      uses: actions/github-script@v7
+      with:
+        script: |
+          const noFiles = '${{ steps.check-files.outputs.no-files }}';
+          const changesMade = '${{ steps.format.outputs.changes-made }}';
+          const filesProcessed = '${{ steps.format.outputs.files-processed }}';
+          const filesChanged = '${{ steps.format.outputs.files-changed }}';
+          const blocksFormatted = '${{ steps.format.outputs.total-blocks-formatted }}';
+          
+          let body;
+          
+          if (noFiles === 'true') {
+            body = [
+              '## 🔍 Code Style Check Results',
+              '',
+              '✅ **No markdown files were changed in this PR.**',
+              '',
+              'The code style checker found no markdown files to process.',
+              '',
+              '---',
+              '',
+              '🤖 *This comment was automatically generated by the [Code Style Formatter](https://github.com/QuantEcon/meta/.github/actions/code-style-checker).*'
+            ].join('\n');
+          } else if (changesMade === 'true') {
+            body = [
+              '## ✅ Code Style Formatting Applied',
+              '',
+              `🎉 **Successfully applied black formatting to ${blocksFormatted} code block(s) across ${filesChanged} file(s).**`,
+              '',
+              '**Summary:**',
+              `- **Files processed:** ${filesProcessed}`,
+              `- **Files modified:** ${filesChanged}`,
+              `- **Code blocks formatted:** ${blocksFormatted}`,
+              '',
+              '**Changes committed:**',
+              '- Each modified file has been committed separately with a descriptive commit message',
+              '- The formatting follows PEP8 standards using black',
+              '',
+              '**Languages processed:**',
+              '- \`python\`, \`python3\`, \`ipython\`, \`ipython3\` code blocks',
+              '- Both MyST \`{code-cell}\` directives and standard markdown fenced code blocks',
+              '',
+              '---',
+              '',
+              '🤖 *This comment was automatically generated by the [Code Style Formatter](https://github.com/QuantEcon/meta/.github/actions/code-style-checker).*'
+            ].join('\n');
+          } else {
+            body = [
+              '## ✅ Code Style Check Completed',
+              '',
+              `📝 **Processed ${filesProcessed} markdown file(s) - no formatting changes needed.**`,
+              '',
+              'All Python code blocks in the changed markdown files are already properly formatted according to PEP8 standards.',
+              '',
+              '**Summary:**',
+              `- **Files processed:** ${filesProcessed}`,
+              '- **Files modified:** 0',
+              '- **Code blocks formatted:** 0',
+              '',
+              '**Languages checked:**',
+              '- \`python\`, \`python3\`, \`ipython\`, \`ipython3\` code blocks',
+              '- Both MyST \`{code-cell}\` directives and standard markdown fenced code blocks',
+              '',
+              '---',
+              '',
+              '🤖 *This comment was automatically generated by the [Code Style Formatter](https://github.com/QuantEcon/meta/.github/actions/code-style-checker).*'
+            ].join('\n');
+          }
+          
+          await github.rest.issues.createComment({
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            issue_number: context.issue.number,
+            body: body
+          });
 ```
 
 ## Inputs