derivation {
name = "filter";
system = "@system@";
builder = "@shell@";
args = ["-e" "-x" (builtins.toFile "builder" "PATH=@testPath@; ln -s $input $out")];
input =
let filter = path: type: type != "symlink" && baseNameOf (toString path) != "foo";
in builtins.filterSource filter ./test-tmp/filterin;
}