Send update instructions after project namespace id changed or namespace path changed

app/mailers/notify.rb

@@ -102,6 +102,12 @@ class Notify < ActionMailer::Base
   end
 
 
+  def project_was_moved_email(user_project_id)
+    @users_project = UsersProject.find user_project_id
+    @project = @users_project.project
+    mail(to: @users_project.user.email,
+         subject: subject("project was moved"))
+  end
 
   #
   # User

app/models/namespace.rb

@@ -59,7 +59,10 @@ class Namespace < ActiveRecord::Base
       if File.exists?(new_path)
         raise "Already exists"
       end
-      system("mv #{old_path} #{new_path}")
+
+      if system("mv #{old_path} #{new_path}")
+        send_update_instructions
+      end
     end
   end
 
@@ -67,4 +70,8 @@ class Namespace < ActiveRecord::Base
     dir_path = File.join(Gitlab.config.gitolite.repos_path, path)
     system("rm -rf #{dir_path}")
   end
+
+  def send_update_instructions
+    projects.each(&:send_move_instructions)
+  end
 end

app/models/project.rb

@@ -259,4 +259,10 @@ class Project < ActiveRecord::Base
       merge_requests
     end
   end
+
+  def send_move_instructions
+    self.users_projects.each do |member|
+      Notify.project_was_moved_email(member.id).deliver
+    end
+  end
 end

app/observers/project_observer.rb

@@ -3,7 +3,8 @@ class ProjectObserver < ActiveRecord::Observer
     project.update_repository
   end
 
-  def after_save(project)
+  def after_update(project)
+    project.send_move_instructions if project.namespace_id_changed?
   end
 
   def after_destroy(project)

app/views/notify/project_was_moved_email.html.haml

+%td.content{align: "left", style: "font-family: Helvetica, Arial, sans-serif; padding: 20px 0 0;", valign: "top", width: "600"}
+  %table{border: "0", cellpadding: "0", cellspacing: "0", style: "color: #555; font: normal 11px Helvetica, Arial, sans-serif; margin: 0; padding: 0;", width: "600"}
+    %tr
+      %td{width: "21"}
+      %td
+        %h3
+          = "Project was moved in another location"
+      %td{width: "21"}
+    %tr
+      %td{width: "21"}
+      %td
+        %p
+          Project is now accessible via next link
+          = link_to project_url(@project) do
+            = @project.name_with_namespace
+        %p
+          You may want to update your local repository with new remote:
+        %br
+        %table{border: "0", cellpadding: "0", cellspacing: "0", width: "558"}
+          %tr
+            %td{valign: "top"}
+              %p{ style: "background:#f5f5f5; padding:10px; border:1px solid #ddd" }
+                git remote set-url origin #{@project.ssh_url_to_repo}
+        %br
+      %td{ width: "21"}