Replace hardcoded string "diff" in Repositories_Helper (#9043).

Contributed by Tom Rochette.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@6424 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/helpers/repositories_helper.rb

@@ -103,7 +103,7 @@ module RepositoriesHelper
                              :path => path_param,
                              :rev => @changeset.identifier) unless c.action == 'D'
         text << " - #{h(c.revision)}" unless c.revision.blank?
-        text << ' (' + link_to('diff', :controller => 'repositories',
+        text << ' (' + link_to(l(:label_diff), :controller => 'repositories',
                                        :action => 'diff',
                                        :id => @project,
                                        :path => path_param,