Function read_until 

pub fn read_until(
    store: &Rc<dyn DurableStore>,
    package: &str,
    room: &str,
    origin: &Origin,
    heads: &[ChangeHash],
) -> Result<AutoCommit, TransferError>

read as of heads: what the document held before its app stamped it retired, which is everything a move still has to bring along.

Errors

As read, and heads the stored document does not contain.