Allow unscope to work with `where.not`

Allows you to call #unscope on a relation with negative equality operators,
i.e. Arel::Nodes::NotIn and Arel::Nodes::NotEqual that have been generated
through the use of where.not.

activerecord/CHANGELOG.md

+*   `ActiveRecord::QueryMethods#unscope` unscopes negative equality
+
+    Allows you to call `#unscope` on a relation with negative equality 
+    operators, i.e. `Arel::Nodes::NotIn` and `Arel::Nodes::NotEqual` that have
+    been generated through the use of `where.not`.
+    
+    *Eric Hankins*
+    
 *   Raise an exception when model without primary key calls `.find_with_ids`.
 
     *Shimpei Makimoto*

activerecord/lib/active_record/relation/query_methods.rb

@@ -856,7 +856,7 @@ def where_unscoping(target_value)
 
       where_values.reject! do |rel|
         case rel
-        when Arel::Nodes::In, Arel::Nodes::Equality
+        when Arel::Nodes::In, Arel::Nodes::NotIn, Arel::Nodes::Equality, Arel::Nodes::NotEqual
           subrelation = (rel.left.kind_of?(Arel::Attributes::Attribute) ? rel.left : rel.right)
           subrelation.name.to_sym == target_value_sym
         else

activerecord/test/cases/scoping/default_scoping_test.rb

@@ -122,17 +122,25 @@ def test_unscope_after_reordering_and_combining
   end
 
   def test_unscope_with_where_attributes
-    expected = Developer.order('salary DESC').collect { |dev| dev.name }
-    received = DeveloperOrderedBySalary.where(name: 'David').unscope(where: :name).collect { |dev| dev.name }
+    expected = Developer.order('salary DESC').collect(&:name)
+    received = DeveloperOrderedBySalary.where(name: 'David').unscope(where: :name).collect(&:name)
     assert_equal expected, received
 
-    expected_2 = Developer.order('salary DESC').collect { |dev| dev.name }
-    received_2 = DeveloperOrderedBySalary.select("id").where("name" => "Jamis").unscope({:where => :name}, :select).collect { |dev| dev.name }
+    expected_2 = Developer.order('salary DESC').collect(&:name)
+    received_2 = DeveloperOrderedBySalary.select("id").where("name" => "Jamis").unscope({:where => :name}, :select).collect(&:name)
     assert_equal expected_2, received_2
 
-    expected_3 = Developer.order('salary DESC').collect { |dev| dev.name }
-    received_3 = DeveloperOrderedBySalary.select("id").where("name" => "Jamis").unscope(:select, :where).collect { |dev| dev.name }
+    expected_3 = Developer.order('salary DESC').collect(&:name)
+    received_3 = DeveloperOrderedBySalary.select("id").where("name" => "Jamis").unscope(:select, :where).collect(&:name)
     assert_equal expected_3, received_3
+    
+    expected_4 = Developer.order('salary DESC').collect(&:name)
+    received_4 = DeveloperOrderedBySalary.where.not("name" => "Jamis").unscope(where: :name).collect(&:name)
+    assert_equal expected_4, received_4
+    
+    expected_5 = Developer.order('salary DESC').collect(&:name)
+    received_5 = DeveloperOrderedBySalary.where.not("name" => ["Jamis", "David"]).unscope(where: :name).collect(&:name)
+    assert_equal expected_5, received_5
   end
 
   def test_unscope_multiple_where_clauses