Git is not a blockchain. An audit log doesn't need to be blockchain. The whole point of blockchain is that is is decentralized, trust-less and permission-less. You take it away and what is left?
That is largely an issue of nomenclature, but there is a school of thought that distinguishes between public, open, trust-less blockchains (which then need a consensus mechanism), and private, permissioned blockchains (which have a central authority and thus don't need a consensus mechanism).
Whether the latter has many use cases is a good question, but git certainly fits the definition.
