fix(coprocessor): skip coverage PR comment when diff is N/A (#2207)

fix(coprocessor): skip coverage PR comment when diff is N/A or no rust files changed

Author: PanGan21

.github/workflows/coprocessor-cargo-tests.yml

@@ -241,8 +241,8 @@ jobs:
         DIFF_PCT: ${{ steps.diff-cov.outputs.diff_pct }}
       run: |
         {
-          echo '### Changed Lines Coverage'
-          echo "Coverage of added/modified lines: **${DIFF_PCT}**"
+          echo '### Coprocessor Changed Lines Coverage'
+          echo "Coverage of added/modified lines in \`coprocessor\`: **${DIFF_PCT}**"
           echo ''
           if [ -f /tmp/diff-cover-report.md ]; then
             echo '<details><summary>Per-file breakdown</summary>'
@@ -254,7 +254,7 @@ jobs:
         } | tee -a "$GITHUB_STEP_SUMMARY" > /tmp/coverage-comment.md
 
     - name: Post coverage comment on PR
-      if: ${{ !cancelled() && github.event.pull_request.head.repo.full_name == github.repository }}
+      if: ${{ !cancelled() && github.event.pull_request.head.repo.full_name == github.repository && steps.diff-cov.outputs.diff_pct != 'N/A' }}
       uses: marocchino/sticky-pull-request-comment@773744901bac0e8cbb5a0dc842800d45e9b2b405 # v2.9.4
       with:
         path: /tmp/coverage-comment.md