Compare link for branches

app/helpers/compare_helper.rb

@@ -3,6 +3,7 @@ module CompareHelper
     params[:from].present? && params[:to].present? &&
       @repository.branch_names.include?(params[:from]) &&
       @repository.branch_names.include?(params[:to]) &&
+      params[:from] != params[:to] &&
       !@refs_are_same
   end

app/views/projects/branches/_branch.html.haml

@@ -13,6 +13,10 @@
         = link_to archive_project_repository_path(@project, ref: branch.name), class: 'btn grouped btn-small' do
           %i.icon-download-alt
           Download
+      = link_to project_compare_index_path(@project, from: branch.name, to: branch.name), class: 'btn grouped btn-small', title: "Compare" do
+        %i.icon-copy
+        Compare
+
       - if can?(current_user, :admin_project, @project) && branch.name != @repository.root_ref
         = link_to project_branch_path(@project, branch.name), class: 'btn grouped btn-small remove-row', method: :delete, confirm: 'Removed branch cannot be restored. Are you sure?', remote: true do
           %i.icon-trash