default.nix

let
  callFlake = import ./call-flake.nix;
in
# ref can either be expressed as an attribute set or a path to source tree
ref: let
  # if expressed as attribute set, a dir argument may be added to point to a subref
  dir = ref.dir or "";
  src =
    if builtins.isPath ref || builtins.isString ref
    then { outPath = ref; }
    else builtins.fetchTree (
      if builtins.isAttrs ref
      then builtins.removeAttrs ref ["dir"]
      else ref
    );
  lockstr = let
    rootlock = "${src}/flake.lock";
    sublock = "${src}/${dir}/flake.lock";
  in
    if dir == "" && builtins.pathExists rootlock
    then builtins.readFile rootlock
    else if dir != "" && builtins.pathExists sublock
    then builtins.readFile sublock
    else
      builtins.toJSON {
        nodes.root = {};
        root = "root";
      };
in
  callFlake lockstr { root = { sourceInfo = src; subdir = dir; }; }