Add & update specs for CODEOWNER parsing

The patterns are now built differently so the specs are updated to
reflect that.

Added a spec to make sure we're not accidentally matching partial
folder names.

ee/lib/gitlab/code_owners/file.rb

@@ -73,11 +73,10 @@ module Gitlab
       end
 
       def path_matches?(pattern, path)
+        # `FNM_DOTMATCH` makes sure we also match files starting with a `.`
+        # `FNM_PATHNAME` makes sure ** matches path separators
         flags = ::File::FNM_DOTMATCH | ::File::FNM_PATHNAME
 
-        # Then the pattern ends in a wildcard, we only want to go one level deep
-        # setting `::File::FNM_PATHNAME` makes the `*` not match directory
-        # separators
         ::File.fnmatch?(pattern, path, flags)
       end
     end

ee/spec/lib/gitlab/code_owners/file_spec.rb

@@ -17,15 +17,15 @@ describe Gitlab::CodeOwners::File do
   describe '#parsed_data' do
     it 'parses all the required lines' do
       expected_patterns = [
-        '*', '**#file_with_pound.rb', '*.rb', '**CODEOWNERS', '**LICENSE', 'docs/',
-        'docs/*', 'config/', '**lib/', '**path with spaces/'
+        '/**/*', '/**/#file_with_pound.rb', '/**/*.rb', '/**/CODEOWNERS', '/**/LICENSE', '/docs/**/*',
+        '/docs/*', '/config/**/*', '/**/lib/**/*', '/**/path with spaces/**/*'
       ]
       expect(file.parsed_data.keys)
         .to contain_exactly(*expected_patterns)
     end
 
     it 'allows usernames and emails' do
-      expect(file.parsed_data['**LICENSE']).to include('legal', 'janedoe@gitlab.com')
+      expect(file.parsed_data['/**/LICENSE']).to include('legal', 'janedoe@gitlab.com')
     end
 
     context 'when there are entries that do not look like user references' do
@@ -34,7 +34,7 @@ describe Gitlab::CodeOwners::File do
       end
 
       it 'ignores the entries' do
-        expect(file.parsed_data['**a-path/']).to include('username', 'email@gitlab.org')
+        expect(file.parsed_data['/**/a-path/**/*']).to include('username', 'email@gitlab.org')
       end
     end
   end
@@ -178,5 +178,22 @@ describe Gitlab::CodeOwners::File do
         expect(owners).to be_nil
       end
     end
+
+    context 'partial matches' do
+      let(:file_content) do
+        'foo/* @user-1 @user-2'
+      end
+
+      it 'does not match a file in a folder that looks the same' do
+        owners = file.owners_for_path('fufoo/bar')
+
+        expect(owners).to be_nil
+      end
+
+      it 'matches the file in any folder' do
+        expect(file.owners_for_path('baz/foo/bar')).to include('user-1', 'user-2')
+        expect(file.owners_for_path('/foo/bar')).to include('user-1', 'user-2')
+      end
+    end
   end
 end