Constant REGISTRATIONS_FILE 

pub const REGISTRATIONS_FILE: &'static str;

What a .yog registers when the game starts — content the game can’t add or change while it runs (blocks, items, entity types, sound groups, materials, dimensions): a line each, <kind> <id> <hash>, the hash of what can’t change. A hot reload compares the new .yog’s with what’s registered (registration_changes).