Keep branch/tag when navigate from commits to tree

app/views/layouts/project.html.haml

@@ -28,7 +28,7 @@
 
               - if @project.repo_exists?
                 = link_to "Repository", project_repository_path(@project), :class => repository_tab_class
-                = link_to "Tree", tree_project_ref_path(@project,  @project.root_ref), :class => tree_tab_class
+                = link_to "Tree", tree_project_ref_path(@project, @ref || @project.root_ref), :class => tree_tab_class
                 = link_to "Commits", project_commits_path(@project), :class => (controller.controller_name == "commits") ? "current" : nil
                 = link_to "Network", graph_project_path(@project), :class => current_page?(:controller => "projects", :action => "graph", :id => @project) ? "current" : nil
                 = link_to  project_issues_filter_path(@project), :class => (controller.controller_name == "issues") ? "current" : nil do