testers.invalidateFetcherByDrvHash: salt pname if presented

      drvPath = (f args).drvPath;

      # It's safe to discard the context, because we don't access the path.

      salt = builtins.unsafeDiscardStringContext (lib.substring 0 12 (baseNameOf drvPath));

      saltName = name: "${name}-salted-${salt}";

      getSaltedNames =

        args:

        if args.pname or null != null then

          { pname = saltName args.pname; }

        else

          { name = saltName args.name or "source"; };

      # New derivation incorporating the original drv hash in the name

      salted = f (args // { name = "${args.name or "source"}-salted-${salt}"; });

      salted = f (args // getSaltedNames args);

      # Make sure we did change the derivation. If the fetcher ignores `name`,

      # `invalidateFetcherByDrvHash` doesn't work.

      checked =