Add CHANGELOG entry for #14861 and document private methods on the API

activemodel/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   Added `rollback_changes` method to `ActiveModel::Dirty` API to roolback all the
+    changed values to the previous data.
+
+    *Igor G.*
+
 *   Allow proc and symbol as values for `only_integer` of `NumericalityValidator`
 
     *Robin Mehner*

activemodel/lib/active_model/dirty.rb

@@ -179,19 +179,19 @@ module ActiveModel
     private
 
       # Removes current changes and makes them accessible through +previous_changes+.
-      def changes_applied
+      def changes_applied # :doc:
         @previously_changed = changes
         @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
       end
 
-      # Removes all dirty data: current changes and previous changes
-      def reset_changes
+      # Removes all dirty data: current changes and previous changes.
+      def reset_changes # :doc:
         @previously_changed = ActiveSupport::HashWithIndifferentAccess.new
         @changed_attributes = ActiveSupport::HashWithIndifferentAccess.new
       end
 
-      # Restore all previous data
-      def rollback_changes #:doc:
+      # Restore all previous data.
+      def rollback_changes # :doc:
         changed_attributes.each_key { |attr| reset_attribute! attr }
       end