Merge branch 'add-one-line-upgrader-command' into 'master'

Add One Line Upgrader Command

This is related to my previous MR from one month ago. I've done a fresh checkout of master and reapplied the path so that the tree is clean again, as requested.

doc/update/upgrader.md

@@ -40,3 +40,10 @@ To make sure you didn't miss anything run a more thorough check with:
     sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production
     
 If all items are green, then congratulations upgrade is complete!
+
+
+### One line upgrade command
+
+You've read through the entire guide, and probably did all the steps manually. Here is a one liner for convenience, the next time you upgrade:
+
+    cd /home/git/gitlab; sudo -u git -H bundle exec rake gitlab:backup:create RAILS_ENV=production; sudo service gitlab stop; sudo -u git -H ruby script/upgrade.rb -y; sudo service gitlab start; sudo service nginx restart; sudo -u git -H bundle exec rake gitlab:check RAILS_ENV=production