Add the group path to the issue ID if applicable

app/models/project.rb

@@ -591,10 +591,18 @@ class Project < ActiveRecord::Base
     end
   end
 
-  def to_reference(from_project = nil, full: false)
-    if full || cross_namespace_reference?(from_project)
-      path_with_namespace
-    elsif cross_project_reference?(from_project)
+  def to_reference(from_project = nil, from_group = nil)
+    if from_group.nil?
+      if cross_namespace_reference?(from_project)
+        path_with_namespace
+      elsif cross_project_reference?(from_project)
+        path
+      elsif self == from_project
+        nil
+      else
+        path_with_namespace
+      end
+    else
       path
     end
   end

app/views/projects/issues/_issue.html.haml

@@ -34,7 +34,7 @@
           = note_count
 
   .issue-info
-    #{issue.to_reference} ·
+    #{issue.to_reference(@project, @group)} ·
     opened #{time_ago_with_tooltip(issue.created_at, placement: 'bottom')}
     by #{link_to_member(@project, issue.author, avatar: false)}
     - if issue.milestone