Merge branch 'issue_13501' into 'master'

Add link to open merge requests on label index

Closes #13501 

See merge request !3057

app/models/label.rb

@@ -27,6 +27,7 @@ class Label < ActiveRecord::Base
   belongs_to :project
   has_many :label_links, dependent: :destroy
   has_many :issues, through: :label_links, source: :target, source_type: 'Issue'
+  has_many :merge_requests, through: :label_links, source: :target, source_type: 'MergeRequest'
 
   validates :color, color: true, allow_blank: false
   validates :project, presence: true, unless: Proc.new { |service| service.template? }
@@ -90,6 +91,10 @@ class Label < ActiveRecord::Base
     issues.closed.count
   end
 
+  def open_merge_requests_count
+    merge_requests.opened.count
+  end
+
   def template?
     template
   end

app/views/projects/labels/_label.html.haml

@@ -2,6 +2,10 @@
   = render "shared/label_row", label: label
 
   .pull-right
+    %strong.append-right-20
+      = link_to_label(label, type: :merge_request) do
+        = pluralize label.open_merge_requests_count, 'open merge request'
+
     %strong.append-right-20
       = link_to_label(label) do
         = pluralize label.open_issues_count, 'open issue'