Whatever happened to SHA-256 support in Git?

My first thought was to prefix hashes with the hash type and a separator, e.g. "sha256:0123...". That way you could add new hashes whenever the devs wanted, by just adding the algorithm and assigning a new prefix. Any hash already stored inside a git repo that is not preceded by a type is automatically assumed to be sha1. A commit with an sha256 hash could have parents with either sha256 or sha1 hashes, or even both!

The way they decided to go about things (last I checked) did seem a bit constraining.