Moodle upgrade from 3.11 to 4.0

Decided to do this upgrade from the command line. So,

sudo zip -r /path/to/data_disk/site_old.zip /var/www/site_old

etc to take a backup, then

sudo -u www-data /usr/bin/php admin/cli/maintenance.php --enable

git fetch

git branch --track MOODLE_400_STABLE origin/MOODLE_400_STABLE

git stash

git checkout MOODLE_400_STABLE

sudo chown -R azureuser:www-data *

sudo -u www-data /usr/bin/php admin/cli/upgrade.php

sudo -u www-data /usr/bin/php admin/cli/maintenance.php --disable

On one of our sites which had the Enlightlite theme, after the upgrade, the login page was completely black. So, deleted the /theme/enlightlite directory, which forced the default theme, and then from the web interface, installed the updated version of the theme, all OK. 

(

Since we had upgraded using git earlier, just did a trial run using

git clone /path/to/source /path/to/destination

cd /path/to/destination

git remote set-url origin git://git.moodle.org/moodle.git

but 

git branch -r still showed only the 311 branch, no 400 branch.

Then, did

git fetch

which then allowed me to do 

git branch --track MOODLE_400_STABLE origin/MOODLE_400_STABLE

git checkout MOODLE_400_STABLE

)

References: 
https://devconnected.com/how-to-change-git-remote-origin/

https://docs.moodle.org/400/en/Git_for_Administrators

https://moodle.org/mod/forum/discuss.php?d=325116