ci: dump regressions head of diff to log

If there are regressions dump the number of changes and the head
of the diff file so one doesn't have to search in the artifacts
for a quick look at the problem.

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>

ci/run_test_suite.sh

@@ -154,6 +154,9 @@ interpret_results()
 
          1)
          echo "Fail - diff against previous results: $RESULTS_DIR/regression_diff.txt"
+         echo -n "Changes detected: "
+         grep ^+ $RESULTS_DIR/regression_diff.txt | wc -l 
+         head -n20 $RESULTS_DIR/regression_diff.txt
          return 1
          ;;