Use metadata stored in artifacats metadata file

app/controllers/projects/artifacts_controller.rb

@@ -18,8 +18,8 @@ class Projects::ArtifactsController < Projects::ApplicationController
     return render_404 unless build.artifacts?
 
     current_path = params[:path] ? "./#{params[:path]}/" : './'
-    artifacts_metadata = build.artifacts_metadata_for(current_path)
-    @path = Gitlab::StringPath.new(current_path, artifacts_metadata)
+    metadata = build.artifacts_metadata_for_path(current_path)
+    @path = Gitlab::StringPath.new(current_path, metadata)
   end
 
   private

app/models/ci/build.rb

@@ -349,8 +349,23 @@ module Ci
       artifacts? && artifacts_file.path.end_with?('zip') && artifacts_metadata.exists?
     end
 
-    def artifacts_metadata_for(path)
-      {}
+    def artifacts_metadata_for_path(path)
+      return {} unless artifacts_metadata.exists?
+      metadata = []
+      meta_path = path.sub(/^\.\//, '')
+
+      File.open(artifacts_metadata.path) do |file|
+        gzip = Zlib::GzipReader.new(file)
+        gzip.each_line do |line|
+          if line =~ %r{^#{meta_path}[^/]+/?\s}
+            path, meta = line.split(' ')
+            metadata << path
+          end
+        end
+        gzip.close
+      end
+
+      metadata
     end
 
     private

lib/gitlab/string_path.rb

@@ -5,7 +5,7 @@ module Gitlab
   # This is IO-operations safe class, that does similar job to 
   # Ruby's Pathname but without the risk of accessing filesystem.
   #
-  # TODO: better support for '../' and './'
+  # TODO, better support for '../' and './'
   #
   class StringPath
     attr_reader :path, :universe