add comparison to master branch

.github/workflows/MLPipelinePullRequest.yml

@@ -73,8 +73,10 @@ jobs:
       run: |
         cd modules/ml-pipeline/src/pipeline/src
         echo "## Model metrics" > report.md
-        cat metrics/metrics.json >> report.md
-        cml comment create report.md
+
+        # Compare metrics to main
+        git fetch --depth=1 origin main:main
+        dvc metrics diff --show-md main >> report.md
 
     #     # echo "## Residuals plot from model" >> report.md
     #     # metrics_location=$(find . -maxdepth 10 -name "residuals.png")