tree view need use ascii-8bit, file name need be utf8.

app/helpers/tree_helper.rb

@@ -18,6 +18,7 @@ module TreeHelper
   end
 
   def tree_full_path(content)
+    content.name.force_encoding('utf-8')
     if params[:path]
       File.join(params[:path], content.name)
     else

app/models/tree.rb

@@ -16,7 +16,7 @@ class Tree
   def initialize(raw_tree, project, ref = nil, path = nil)
     @project, @ref, @path = project, ref, path,
     @tree = if path
-              raw_tree / path
+              raw_tree / path.dup.force_encoding('ascii-8bit')
             else
               raw_tree
             end

app/views/refs/_tree_file.html.haml

@@ -2,7 +2,7 @@
   .file_title
     %i.icon-file
     %span.file_name
-      = name
+      = name.force_encoding('utf-8')
       %small #{file.mode}
     %span.options
       = link_to "raw", blob_project_ref_path(@project, @ref, path: params[:path]), class: "btn very_small", target: "_blank"