fix increase_parent_counter_cache callback

no longer incrementing counter when callbacks are disabled (to make increase and decrease consistent)

Update parent_counter_cache now respects @_trigger_update_callback

Not sure if update follows the same rules as destroy introduced in 63b42f5
But would like both trees to follow the same logic

There are reports of incorrect cache counts. So when insert and destroy have different
guard clauses, it is suspect.

lib/ancestry/instance_methods.rb

@@ -62,6 +62,7 @@ def touch_ancestors_callback
 
     # Counter Cache
     def increase_parent_counter_cache
+      return if ancestry_callbacks_disabled?
       self.ancestry_base_class.increment_counter _counter_cache_column, parent_id
     end
 
@@ -78,14 +79,18 @@ def decrease_parent_counter_cache
     end
 
     def update_parent_counter_cache
-      changed = saved_change_to_attribute?(self.ancestry_base_class.ancestry_column)
-
-      return unless changed
+      # @_trigger_update_callback comes from activerecord, which makes sure only once decrement when concurrent deletion.
+      # but @_trigger_update_callback began after [email protected].
+      # https://github.com/rails/rails/blob/v5.2.0/activerecord/lib/active_record/persistence.rb#L340
+      # https://github.com/rails/rails/pull/27248
+      return if defined?(@_trigger_update_callback) && !@_trigger_update_callback
+      return unless saved_change_to_attribute?(self.ancestry_base_class.ancestry_column)
 
       if parent_id_was = parent_id_before_last_save
         self.ancestry_base_class.decrement_counter _counter_cache_column, parent_id_was
       end
 
+      # TODO: use increase_parent_counter_cache instead?
       parent_id && self.ancestry_base_class.increment_counter(_counter_cache_column, parent_id)
     end