self: super:
let lib = super.lib; in
{
  lib = (super.lib or {}) // {
    findFiles = pattern:
      with builtins;
      let go = curr:
        let dir = readDir curr; in
        let files = lib.filterAttrs (name: type:
          type == "regular" &&
          match pattern name != null) dir; in
        let dirs = lib.filterAttrs (name: type: type == "directory") dir; in
        map (name: "${curr}/${name}") (attrNames files) ++
        lib.concatMap (name: go "${curr}/${name}") (attrNames dirs)
        ;
      in root: go (toPath root);
  };
}