fixes due to review: compare by identity

platform/platform-impl/src/com/intellij/openapi/command/impl/UndoRedo.java

@@ -98,7 +98,7 @@ abstract class UndoRedo {
 
     Set<DocumentReference> clashing = getStackHolder().collectClashingActions(myUndoableGroup);
     if (!clashing.isEmpty()) {
-      UndoableGroup globalUndoableGroup = getStackHolder().findGlobalUndoableGroup(myUndoableGroup.getCommandTimestamp());
+      UndoableGroup globalUndoableGroup = getStackHolder().findGlobalUndoableGroup(myUndoableGroup);
       if (globalUndoableGroup != null) {
         if(isRedo())
           myManager.redo(null);

platform/platform-impl/src/com/intellij/openapi/command/impl/UndoRedoStacksHolder.java

@@ -269,9 +269,9 @@ class UndoRedoStacksHolder {
   }
 
   @Nullable
-  public UndoableGroup findGlobalUndoableGroup(int timestamp) {
+  public UndoableGroup findGlobalUndoableGroup(UndoableGroup timestamp) {
     for (UndoableGroup group : myGlobalStack) {
-      if (group.getCommandTimestamp() == timestamp) {
+      if (group == timestamp) {
         return group;
       }
     }