core/pkgs/build-support/fetchmtn/default.nix

# You can specify some extra mirrors and a cache DB via options
{
  lib,
  stdenvNoCC,
  monotone,
  defaultDBMirrors ? [ ],
  cacheDB ? "./mtn-checkout.db",
}:
# dbs is a list of strings
# each is an url for sync

# selector is mtn selector, like h:org.example.branch
#
{
  name ? "mtn-checkout",
  dbs ? [ ],
  sha256,
  selector ? "h:" + branch,
  branch,
}:

stdenvNoCC.mkDerivation {
  builder = ./builder.sh;
  nativeBuildInputs = [ monotone ];

  outputHashAlgo = "sha256";
  outputHashMode = "recursive";
  outputHash = sha256;

  dbs = defaultDBMirrors ++ dbs;
  inherit
    branch
    cacheDB
    name
    selector
    ;

  impureEnvVars = lib.fetchers.proxyImpureEnvVars;

}