github: update lint.yml to post details on formatting issue (#3988)

before this change, user need to click into the details for more
details on the formatting issue identified by the lint workflow.

after this change, the workflow pastes the details with a comment,
to provide more specific details on the formatting issue if any.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>

.github/workflows/lint.yml

@@ -8,6 +8,7 @@ on:
 
 permissions:
   contents: read
+  pull-requests: write
 
 jobs:
   format_code:
@@ -21,6 +22,34 @@ jobs:
         clangformat: 17.0.5
 
     - name: Run clang-format
+      id: clang_format
       run: |
         find include src -name '*.h' -o -name '*.cc' |  xargs clang-format -i -style=file -fallback-style=none
-        git diff --exit-code
+        git diff | tee fmt.patch
+        if [ -s fmt.patch ]; then
+          exit 1
+        fi
+    - uses: actions/github-script@v7
+      if: failure() && steps.clang_format.outcome == 'failure'
+      with:
+        script: |
+          const fs = require('fs');
+          const patch = fs.readFileSync('fmt.patch', { encoding: 'utf8' });
+          const comment = `clang-format 17.0.5 found issues in the formatting in your code:
+          <details>
+          <summary>
+          View the diff from clang-format:
+          </summary>
+
+          \`\`\`diff
+          ${patch}
+          \`\`\`
+
+          </details>
+          `;
+          await github.rest.issues.createComment({
+            issue_number: context.issue.number,
+            owner: context.repo.owner,
+            repo: context.repo.repo,
+            body: comment
+          });