DiffDB.txt

Use - add to any difficulty level in DiffDB.txt

Gameplay - this flag allows an AI unit in a city that is capable to upgrade to be upgraded without costing gold to the AI.

Elsewise, the code is set up to upgrade AI units as long as they have the gold to do it.

Gold is based on the difference in shieldcost multiplied by the govt's unitrushgoldmodifier cost per shield