Are you logged in as admin. If you are not logged in and trying to access site/core/update.php - I am pretty sure that you will first need to edit the following line in your settings.php file
$settings['update_free_access'] = FALSE; and change it to TRUE
Then change it back when you are done.
[alias] lg = log --color --graph --pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(bold blue)<%an>%Creset' --abbrev-commit
git lg origin/1.xshows what I'm talking about...