Short-circuit logic for NoteDb updates

Change-Id: Ifab161d7b90185e1e60a5421817042cae95c87f8
diff --git a/java/com/googlesource/gerrit/plugins/supermanifest/SuperManifestRefUpdatedListener.java b/java/com/googlesource/gerrit/plugins/supermanifest/SuperManifestRefUpdatedListener.java
index 01d789e..9b14151 100644
--- a/java/com/googlesource/gerrit/plugins/supermanifest/SuperManifestRefUpdatedListener.java
+++ b/java/com/googlesource/gerrit/plugins/supermanifest/SuperManifestRefUpdatedListener.java
@@ -22,6 +22,7 @@
 import com.google.errorprone.annotations.FormatMethod;
 import com.google.errorprone.annotations.FormatString;
 import com.google.gerrit.entities.Project;
+import com.google.gerrit.entities.RefNames;
 import com.google.gerrit.extensions.annotations.PluginName;
 import com.google.gerrit.extensions.api.projects.BranchInput;
 import com.google.gerrit.extensions.config.DownloadScheme;
@@ -299,6 +300,10 @@
       }
       return;
     }
+    if(RefNames.isNoteDbMetaRef(event.getRefName())) {
+      // NoteDb meta ref updates never cause supermanifest updates.
+      return;
+    }
 
     List<ConfigEntry> relevantConfigs =
         findRelevantConfigs(event.getProjectName(), event.getRefName());