The way it works in the current version of git-remote-blossom is that it saves both the sha1 and the sha256 hash in the state event. So a ref tag looks like this:

`["refs/heads/master", "3437fd950d4ba37ba51e3bc788025698cfb20ca1", "3b58e484825e5b96428ab0b0c19cb760d5ebbd39acb4795446a89c99482e2d62"],`

It needs the sha256 to be able to start the graph traversal at the HEAD. All the rest can be calculated.

This is somewhat diverges from the current NIP-34. It needs to be updated with the sha256 - which is right now in the place of the optional parent commit ids.