Settle positions between two mutually non cooperating parties. Your github solution doesn't consider that many non cooperating parties may want to do conflicting things on chain and you need a trustless way to resolve those conflicts. First writer wins to a centralized database at github is not an acceptable settlement method for billion dollar transactions.
EDIT: A blockchain is not just about keeping a history, it's also about maintaining liveness of the chain and preventing censorship even when many non cooperating parties are involved with conflicting incentives.
EDIT: A blockchain is not just about keeping a history, it's also about maintaining liveness of the chain and preventing censorship even when many non cooperating parties are involved with conflicting incentives.