Stop build if coverage is lower than main (#5300)

.github/workflows/build.yaml

@@ -112,6 +112,9 @@ jobs:
             COLOR=green
           fi
 
+          DIFF_RATE=$(echo "$UT_COVERAGE-$MAIN_COVERAGE" | bc -l)
+          echo "diff_coverage=$DIFF_RATE" >> $GITHUB_ENV
+
           echo "coverage_img=https://img.shields.io/badge/coverage-$UT_COVERAGE%25-$COLOR" >> $GITHUB_ENV
           # copy coverage to cache
           cp ./dist/ut_coverage.txt ./dist/cache/
@@ -147,8 +150,14 @@ jobs:
 
             * Your PR branch coverage: ${{ env.ut_coverage }} %
             * main branch coverage: ${{ env.main_coverage }} %
+            * diff coverage: ${{ env.diff_coverage }} %
 
             > The coverage result does not include the functional test coverage. 
+      - name: Stop build if PR branch coverage is lower than main branch.
+        if: (env.main_coverage > env.ut_coverage) &&  matrix.target_arch == 'amd64' && matrix.target_os == 'linux' && github.event.pull_request
+        run: |
+          echo "stop build to prevent from merging PR because coverage is down from ${{ env.main_coverage }} % to ${{ env.ut_coverage }} %."
+          exit 1
       - name: Save coverage (only main push)
         uses: actions/cache/save@v3
         if: matrix.target_arch == 'amd64' && matrix.target_os == 'linux' && github.ref == 'refs/heads/main'