CI: make reporting better

Author: redsun82

.github/workflows/buildifier.yml

@@ -21,10 +21,11 @@ jobs:
       - name: Check bazel formatting
         uses: pre-commit/action@646c83fcd040023954eafda54b4db0192ce70507
         with:
-          extra_args: buildifier --all-files --show-diff-on-failure
-      - name: Print rectifying command
+          extra_args: buildifier --all-files 2>&1 | tee check_output
+      - name: Report
         if: failure()
         run: |
+          sed -ne '/diff --git/,$ p' check_output
           echo "In order to format all bazel files, please run:"
           echo "  bazel run //:buildifier"
           exit 1