Allow specify fixtures to be ignored

Allow specifying what fixtures can be ignored by setting
`ignore` in fixtures YAML file:

    # users.yml
    _fixture:
      ignore:
        - base

    base: &base
      admin: false
      introduction: "This is a default description"

    admin:
      <<: *base
      admin: true

    visitor:
      <<: *base

In the above example, "base" fixture will be ignored when creating
users fixture. This is helpful when you want to inherit attributes
and it makes your fixtures more "DRY".

1 files changed, 5 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/fixture_set/file.rb b/activerecord/lib/active_record/fixture_set/file.rb
index f1ea0e022f..b2030a5bb9 100644
--- a/activerecord/lib/active_record/fixture_set/file.rb
+++ b/activerecord/lib/active_record/fixture_set/file.rb
@@ -29,6 +29,10 @@ module ActiveRecord
         config_row["model_class"]
       end
 
+      def ignored_fixtures
+        config_row["ignore"]
+      end
+
       private
         def rows
           @rows ||= raw_rows.reject { |fixture_name, _| fixture_name == "_fixture" }
@@ -40,7 +44,7 @@ module ActiveRecord
             if row
               row.last
             else
-              { 'model_class': nil }
+              { 'model_class': nil, 'ignore': nil }
             end
           end
         end