def origin.at
import ezx@1.11.0.0/src/lock/lock.bend as Lockimport Base
309# this origin's source when the hash matches, otherwise whatever the rest gave
310def origin.at(known: Origin, rest: Src, wanted: String) -> Src:
311 Origin{n, s} = known
312 Bool.pick(Src, String.eq(n, wanted), s, rest)