title: automaticallyMergesChangesFromParent doesn't do anything
body: <p>I was watching a WWDC 2016 (What's new in Core Data) video about some "new" changes and at some point it's said that this new property <code>automaticallyMergesChangesFromParent</code> is supposed to automatically merge the changes from the parent on the child context.</p>
  
  <p>I created a simple test case:</p>
  
  <pre><code>CustomObject *customObject = [[CustomObject alloc] initWithContext:self.persistentContainer.viewContext];
  customObject.name = @"TEST";
  customObject.customID = 2252;
  self.persistentContainer.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy;
  
  NSManagedObjectContext *firstContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
  firstContext.parentContext = self.persistentContainer.viewContext;
  firstContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy;
  firstContext.automaticallyMergesChangesFromParent = YES;
  
  CustomObject *contextObj = [firstContext objectWithID:customObject.objectID];
  NSLog(@"NAME [%@]", contextObj.name);
  customObject.name = @"JO";
  [self.persistentContainer.viewContext save:NULL];
  NSLog(@"NAME [%@]", contextObj.name);
  </code></pre>
  
  <p>The output is:</p>
  
  <pre><code> NAME [TEST]
   NAME [TEST]
  </code></pre>
  
  <p>I was hoping it would be:</p>
  
  <pre><code>NAME [TEST]
  NAME [JO]
  </code></pre>
  
  <p>if I use a <code>[firstContext refreshAllObjects];</code> it will work as I expect, but it makes not difference if <code>automaticallyMergesChangesFromParent</code> is set to YES or NO.</p>
  
  <p>Am I missing something on how this is supposed to work? The <a href="https://developer.apple.com/documentation/coredata/nsmanagedobjectcontext/1845237-automaticallymergeschangesfrompa" rel="nofollow noreferrer">documentation</a> doesn't help much.</p>
  
  <p>Thanks.</p>