Motivation for this change

The function recursiveUpdateUntil did not produce the expected result for the exact example given in the documentation.

This fixes that and makes the function useable for any predicate that actually looks at the path argument. In current nixpkgs, there is only 1 location that touches this functionality:

I'm not fully sure what that is all about, but since it's maintainer-only I do not expect issues will arise because of this fix, as they probably just assumed this function worked as advertised as well.

$ nix repl lib
Welcome to Nix version 2.0.2. Type :? for help.

Loading 'lib'...
Added 350 variables.

-- this is the exact example from the function's documentation:
nix-repl> recursiveUpdateUntil (path: l: r: path == ["foo"]) {
                   # first attribute set
                   foo.bar = 1;
                   foo.baz = 2;
                   bar = 3;
                 } {
                   #second attribute set
                   foo.bar = 1;
                   foo.quz = 2;
                   baz = 4;
                 }
{ bar = 3; baz = 4; foo = { bar = 1; baz = 2; quz = 2; }; }

-- although the documentation says:
{
    foo.bar = 1; # 'foo.*' from the second set
    foo.quz = 2; #
    bar = 3;     # 'bar' from the first set
    baz = 4;     # 'baz' from the second set
}

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.