Fix regression on after_commit in nested transactions.

after_commit should not run in nested transactions, however they should
run once the outermost transaction gets committed. This patch fixes the
problem copying the records from the Savepoint to its parent. So the
RealTransaction will have all records that needs to run callbacks on it.

[fixes #16425]

activerecord/CHANGELOG.md

@@ -1,3 +1,9 @@
+*   Fix regression on after_commit that didnt fire when having nested transactions.
+
+    Fixes #16425
+
+    *arthurnn*
+
 *   Do not try to write timestamps when a table has no timestamps columns.
 
     Fixes #8813.

activerecord/lib/active_record/connection_adapters/abstract/transaction.rb

@@ -111,6 +111,8 @@ module ActiveRecord
       def commit
         super
         connection.release_savepoint(savepoint_name)
+        parent = connection.transaction_manager.current_transaction
+        records.each { |r| parent.add_record(r) }
       end
 
       def full_rollback?; false; end

activerecord/test/cases/transaction_callbacks_test.rb

@@ -129,6 +129,19 @@ class TransactionCallbacksTest < ActiveRecord::TestCase
     assert_equal [:commit_on_update], @first.history
   end
 
+  def test_only_call_after_commit_on_top_level_transactions
+    @first.after_commit_block{|r| r.history << :after_commit}
+    assert @first.history.empty?
+
+    @first.transaction do
+      @first.transaction(requires_new: true) do
+        @first.touch
+      end
+      assert @first.history.empty?
+    end
+    assert_equal [:after_commit], @first.history
+  end
+
   def test_call_after_rollback_after_transaction_rollsback
     @first.after_commit_block{|r| r.history << :after_commit}
     @first.after_rollback_block{|r| r.history << :after_rollback}