Make 'migrate' clear the schema cache afterward

Without clearing the caches afterward, removals done in migrations would
not be reflected in a separate task in the same process. That is, given
a table with a migration to remove a column, the schema cache would
still reflect that a table has that in something such as the
'db:seed' task:

`rake db:migrate db:seed`
(A common thing to do in a script for a project ala `bin/setup`)

vs

`rake db:migrate && rake db:seed`
(Two processes)

The first would not reflect that the column was removed.
The second would (cache reset).

activerecord/lib/active_record/tasks/database_tasks.rb

@@ -159,6 +159,7 @@ def migrate
         Migrator.migrate(migrations_paths, version) do |migration|
           scope.blank? || scope == migration.scope
         end
+        ActiveRecord::Base.clear_cache!
       ensure
         Migration.verbose = verbose_was
       end

activerecord/test/cases/tasks/database_tasks_test.rb

@@ -309,19 +309,30 @@ def test_drops_testand_development_databases_when_rails_env_is_development
   end
 
   class DatabaseTasksMigrateTest < ActiveRecord::TestCase
+    def setup
+      ActiveRecord::Tasks::DatabaseTasks.migrations_paths = 'custom/path'
+    end
+
+    def teardown
+      ActiveRecord::Tasks::DatabaseTasks.migrations_paths = nil
+    end
+
     def test_migrate_receives_correct_env_vars
       verbose, version = ENV['VERBOSE'], ENV['VERSION']
 
-      ActiveRecord::Tasks::DatabaseTasks.migrations_paths = 'custom/path'
       ENV['VERBOSE'] = 'false'
       ENV['VERSION'] = '4'
 
       ActiveRecord::Migrator.expects(:migrate).with('custom/path', 4)
       ActiveRecord::Tasks::DatabaseTasks.migrate
     ensure
-      ActiveRecord::Tasks::DatabaseTasks.migrations_paths = nil
       ENV['VERBOSE'], ENV['VERSION'] = verbose, version
     end
+
+    def test_migrate_clears_schema_cache_afterward
+      ActiveRecord::Base.expects(:clear_cache!)
+      ActiveRecord::Tasks::DatabaseTasks.migrate
+    end
   end
 
   class DatabaseTasksPurgeTest < ActiveRecord::TestCase