update odoo code from github
or update any repo cloned from github

simply browse to directory which you are looking to update this can be an OCA repo or any other repo cloned using git.

lets update odoo base 

cd /opt/odoo15/odoo   "odoo folder"

then issue the command 

sudo git fetch origin 15.0

sudo git reset --hard origin/15.0

in Odoo
Uninstalling module from terminal