Add issue and merge request count for state filters.

app/helpers/application_helper.rb

@@ -318,4 +318,16 @@ module ApplicationHelper
       profile_key_path(key)
     end
   end
+
+  def state_filters_text_for(entity, project)
+    entity_title = entity.to_s.humanize
+
+    count =
+      if current_controller?(:issues)
+        " (#{project.issues.send(entity).count})"
+      elsif current_controller?(:merge_requests)
+        " (#{project.merge_requests.send(entity).count})"
+      end
+    "#{entity_title}#{count}"
+  end
 end

app/views/shared/_issuable_filter.html.haml

@@ -4,15 +4,15 @@
       %li{class: ("active" if params[:state] == 'opened')}
         = link_to page_filter_path(state: 'opened') do
           %i.fa.fa-exclamation-circle
-          Open
+          #{state_filters_text_for(:opened, @project)}
       %li{class: ("active" if params[:state] == 'closed')}
         = link_to page_filter_path(state: 'closed') do
           %i.fa.fa-check-circle
-          Closed
+          #{state_filters_text_for(:closed, @project)}
       %li{class: ("active" if params[:state] == 'all')}
         = link_to page_filter_path(state: 'all') do
           %i.fa.fa-compass
-          All
+          #{state_filters_text_for(:all, @project)}
 
   .issues-details-filters
     = form_tag page_filter_path(without: [:assignee_id, :author_id, :milestone_id, :label_name]), method: :get, class: 'filter-form' do