Add option to disable username changing

app/controllers/profiles_controller.rb

@@ -51,7 +51,9 @@ class ProfilesController < ApplicationController
   end
 
   def update_username
+    if Gitlab.config.gitlab.username_changing_enabled
       @user.update_attributes(username: params[:user][:username])
+    end
 
     respond_to do |format|
       format.js

app/views/profiles/account.html.haml

@@ -53,7 +53,8 @@
 
 
 
-%fieldset.update-username
+- if Gitlab.config.gitlab.username_changing_enabled
+  %fieldset.update-username
     %legend
       Username
       %small.cred.right

config/gitlab.yml.example

@@ -35,6 +35,7 @@ gitlab:
   ## Project settings
   default_projects_limit: 10
   # signup_enabled: true          # default: false - Account passwords are not sent via the email if signup is enabled.
+  # username_changing_enabled: false # default: true - User can change her username/namespace
 
 ## Gravatar
 gravatar:

config/initializers/1_settings.rb

@@ -53,6 +53,7 @@ Settings.gitlab['support_email']  ||= Settings.gitlab.email_from
 Settings.gitlab['url']        ||= Settings.send(:build_gitlab_url)
 Settings.gitlab['user']       ||= 'gitlab'
 Settings.gitlab['signup_enabled'] ||= false
+Settings.gitlab['username_changing_enabled'] = true if Settings.gitlab['username_changing_enabled'].nil?
 
 Settings['gravatar'] ||= Settingslogic.new({})
 Settings.gravatar['enabled']      = true if Settings.gravatar['enabled'].nil?