Does anyone know if a standard format for sort of tagged-union hash type, something similar as crypt format for passwords? Feels like everyone is needing to support multiple hash types at some point, and basically needs to reinvent that particular wheel again and again.
It isn't too bad to just exhaustively look up provided hashes in all your databases (at least, for Git). You should probably only support 1 primary hash at a time, and 1 additional legacy hash for migration purposes. This makes lookup twice as expensive; for git, this is not usually the slow part (the slow part is 'git status' having to compare the entire local filesystem checkout to the repo).
