Change requre: in config to be relative to the .rubocop.yml file itself

Fixes rubocop#2865

CHANGELOG.md

@@ -11,6 +11,7 @@
 * Fix false positive in `Style/TrailingCommaInArguments` & `Style/TrailingCommaInLiteral` cops with consistent_comma style. ([@meganemura][])
 * [#2861](https://github.com/bbatsov/rubocop/pull/2861): Fix false positive in `Style/SpaceAroundKeyword` for `rescue(...`. ([@rrosenblum][])
 * [#2832](https://github.com/bbatsov/rubocop/issues/2832): `Style/MultilineOperationIndentation` treats operations inside blocks inside other operations correctly. ([@jonas054][])
+* [#2865](https://github.com/bbatsov/rubocop/issues/2865): Change `require:` in config to be relative to the `.rubocop.yml` file itself. ([@ptarjan][])
 
 ## 0.37.2 (11/02/2016)
 
@@ -2002,3 +2003,4 @@
 [@mmcguinn]: https://github.com/mmcguinn
 [@pocke]: https://github.com/pocke
 [@prsimp]: https://github.com/prsimp
+[@ptarjan]: https://github.com/ptarjan

lib/rubocop/config_loader.rb

@@ -35,7 +35,10 @@ def load_file(path)
         resolve_inheritance_from_gems(hash, hash.delete('inherit_gem'))
         resolve_inheritance(path, hash)
 
-        Array(hash.delete('require')).each { |r| require(r) }
+        config_dir = File.dirname(path)
+        Array(hash.delete('require')).each do |r|
+          require(File.join(config_dir, r))
+        end
 
         hash.delete('inherit_from')
         config = Config.new(hash, path)

spec/rubocop/config_loader_spec.rb

@@ -505,5 +505,13 @@
       described_class.configuration_from_file(config_path)
       expect(defined?(MyClass)).to be_truthy
     end
+
+    it 'uses paths relative to the .rubocop.yml, not cwd' do
+      config_path = described_class.configuration_file_for('.')
+      Dir.chdir '..' do
+        described_class.configuration_from_file(config_path)
+        expect(defined?(MyClass)).to be_truthy
+      end
+    end
   end
 end