Use block version of `Hash#fetch` to avoid unnecessary method call

ee/lib/ee/gitlab/ci/config.rb

@@ -27,7 +27,7 @@ module EE
         end
 
         def process_external_files(config, project, opts)
-          sha = opts.fetch(:sha, project.repository.root_ref_sha)
+          sha = opts.fetch(:sha) { project.repository.root_ref_sha }
           ::Gitlab::Ci::External::Processor.new(config, project, sha).perform
         end
       end