Update summary

Author: SergeiPavlov

Orm/Xtensive.Orm/Orm/Session.Persist.cs

@@ -224,7 +224,7 @@ private async ValueTask Persist(PersistReason reason, bool isAsync, Cancellation
     }
 
     /// <summary>
-    /// Temporarily disables all save changes operations (both explicit ant automatic) 
+    /// Temporarily disables all save changes operations (both explicit ant automatic)
     /// for specified <paramref name="target"/>.
     /// Such entity is prevented from being persisted to the database,
     /// when <see cref="SaveChanges"/> is called or query is executed.
@@ -234,34 +234,37 @@ private async ValueTask Persist(PersistReason reason, bool isAsync, Cancellation
     /// all entities that reference <paramref name="target"/> are also pinned automatically.
     /// </summary>
     /// <param name="target">The entity to disable persisting.</param>
-    /// <returns>A special object that controls lifetime of such behavior if <paramref name="target"/> was not previously processed by the method,
-    /// otherwise <see langword="null"/>.</returns>
+    /// <returns>
+    /// A special object that controls lifetime of such behavior if <paramref name="target"/> was not previously processed by the method
+    /// and automatic saving of changes is enabled (<see cref="SessionOptions.AutoSaveChanges"/>),
+    /// otherwise <see langword="null"/>.
+    /// </returns>
     public IDisposable DisableSaveChanges(IEntity target)
     {
       EnsureNotDisposed();
       ArgumentValidator.EnsureArgumentNotNull(target, "target");
+      if (!Configuration.Supports(SessionOptions.AutoSaveChanges))
+        return null; // No need to pin in this case
+
       var targetEntity = (Entity) target;
       targetEntity.EnsureNotRemoved();
-      return Configuration.Supports(SessionOptions.AutoSaveChanges)
-        ? pinner.RegisterRoot(targetEntity.State)
-        : null; // No need to pin in this case
+      return pinner.RegisterRoot(targetEntity.State);
     }
 
     /// <summary>
     /// Temporarily disables only automatic save changes operations before queries, etc.
     /// Explicit call of <see cref="SaveChanges"/> will lead to flush changes anyway.
     /// If save changes is to be performed due to starting a nested transaction or committing a transaction,
     /// active disabling save changes scope will lead to failure.
-    /// <returns>A special object that controls lifetime of such behavior if there is no active scope,
+    /// <returns>A special object that controls lifetime of such behavior if there is no active scope
+    /// and automatic saving of changes is enabled (<see cref="SessionOptions.AutoSaveChanges"/>),
     /// otherwise <see langword="null"/>.</returns>
     /// </summary>
     public IDisposable DisableSaveChanges()
     {
-      if (!Configuration.Supports(SessionOptions.AutoSaveChanges)) {
-        return null; // No need to pin in this case
+      if (!Configuration.Supports(SessionOptions.AutoSaveChanges) || disableAutoSaveChanges) {
+        return null; // No need to pin in these cases
       }
-      if (disableAutoSaveChanges)
-        return null;
 
       disableAutoSaveChanges = true;
       return new Disposable(_ => {
@@ -318,7 +321,7 @@ private void CancelEntitiesChanges()
         newEntity.Update(null);
         newEntity.PersistenceState = PersistenceState.Removed;
       }
-      
+
       foreach (var modifiedEntity in EntityChangeRegistry.GetItems(PersistenceState.Modified)) {
         modifiedEntity.RollbackDifference();
         modifiedEntity.PersistenceState = PersistenceState.Synchronized;