There’s a new DietPi release, but on one of my DietPi systems I followed these instructions on Github and the system is still “stuck” in that branch. How do I get it back on the “production” branch so that it will properly upgrade?
same way 
G_CONFIG_INJECT 'DEV_GITBRANCH=' 'DEV_GITBRANCH=master' /boot/dietpi.txt
dietpi-update -1