{ lib }:

let
  # If not supported, fall back to tryEval, which will fail in the first case.
  safeCatchAll = if (builtins ? catchAll)
    then builtins.catchAll
    else e: (builtins.tryEval e) // { msg = ""; };
in lib.extend (_: lib: {
  # Same as fetchGit but accepts a list of mirror urls
  fetchGitMirror = { urls, ... } @ args:
  let
    cleanArgs = lib.removeAttrs args [ "urls" ];
    fetchUrl = url: builtins.fetchGit (cleanArgs // { inherit url; });
    safeFetch = url: safeCatchAll (fetchUrl url);
    complain = url:
    let
      r = safeFetch url;
    in
      if (r.success) then r
      else lib.warn "cannot fetch ${url}, trying next
      mirror:${builtins.replaceStrings ["\n" ] ["\n> "] ("\n"+r.msg)}" r;
    fetchList = lib.map (url: complain url) urls;
    bad = throw "cannot fetch from any mirror";
    good = lib.findFirst (e: e.success) bad fetchList;
  in good.value;

  maintainers = lib.maintainers // {
    bsc = import ./maintainers.nix;
  };
})