Use alternate SHA for MR pipelines

merge-request-check/merge_review_check.sh

@@ -6,6 +6,12 @@
 #CI_COMMIT_BEFORE_SHA=""
 #CI_COMMIT_SHA=""
 
+# For merge request pipelines, the before SHA is all 0s.
+# Replace with a MR specific variable for these pipelines.
+if [[ $CI_PIPELINE_SOURCE = 'merge_request_event' ]]; then
+	CI_COMMIT_BEFORE_SHA="$CI_MERGE_REQUEST_DIFF_BASE_SHA"
+fi
+
 # If any commands in this scprt fail, exit with a non-zero exit code
 set -e