Revert "Avoid extra scoping when using `Relation#update`"

This reverts commit 0b29a421.

Reason: This introduce a breaking change when you call `update` in a
relation or an association proxy passing the id argument.

Person.books.update(10, title: 'New title')

activerecord/lib/active_record/persistence.rb

@@ -97,11 +97,13 @@ def instantiate(attributes, column_types = {}, &block)
       # When running callbacks is not needed for each record update,
       # it is preferred to use {update_all}[rdoc-ref:Relation#update_all]
       # for updating all records in a single query.
-      def update(id, attributes)
+      def update(id = :all, attributes)
         if id.is_a?(Array)
           id.map { |one_id| find(one_id) }.each_with_index { |object, idx|
             object.update(attributes[idx])
           }
+        elsif id == :all
+          all.each { |record| record.update(attributes) }
         else
           if ActiveRecord::Base === id
             raise ArgumentError,

activerecord/lib/active_record/relation.rb

@@ -337,10 +337,6 @@ def update_all(updates)
       @klass.connection.update stmt, "#{@klass} Update All"
     end
 
-    def update(attributes) # :nodoc:
-      each { |record| record.update(attributes) }
-    end
-
     # Destroys the records by instantiating each
     # record and calling its {#destroy}[rdoc-ref:Persistence#destroy] method.
     # Each object's callbacks are executed (including <tt>:dependent</tt> association options).

activerecord/test/cases/relations_test.rb

@@ -28,9 +28,7 @@ class RelationTest < ActiveRecord::TestCase
 
   class TopicWithCallbacks < ActiveRecord::Base
     self.table_name = :topics
-    cattr_accessor :topic_count
     before_update { |topic| topic.author_name = "David" if topic.author_name.blank? }
-    after_update { |topic| topic.class.topic_count = topic.class.count }
   end
 
   def test_do_not_double_quote_string_id
@@ -1504,8 +1502,6 @@ def test_update_on_relation
     topics = TopicWithCallbacks.where(id: [topic1.id, topic2.id])
     topics.update(title: "adequaterecord")
 
-    assert_equal TopicWithCallbacks.count, TopicWithCallbacks.topic_count
-
     assert_equal "adequaterecord", topic1.reload.title
     assert_equal "adequaterecord", topic2.reload.title
     # Testing that the before_update callbacks have run