{ lib, ... }:

lib.makeExtensible (self: rec {
  mkDate = longDate: lib.concatStringsSep "-" [
    (builtins.substring 0 4 longDate)
    (builtins.substring 4 2 longDate)
    (builtins.substring 6 2 longDate)
  ];
  mkVersionSrc = src: "unstable-" + builtins.substring 0 7 src.rev;
  mkVersionInput = input:
    let
      date = mkDate (input.lastModifiedDate or "19700101");
      rev = input.shortRev or "dirty";
    in
    "unstable-${date}_${rev}}";
})