anchor.diff:        exit 1
       fi
     '' + lib.optionalString revert ''
  -    ${patchutils}/bin/interdiff "$out" /dev/null > "$tmpfile"
  +    ${buildPackages.patchutils}/bin/interdiff "$out" /dev/null > "$tmpfile"
       mv "$tmpfile" "$out"
     '' + (args.postFetch or "");
     meta.broken = excludes != [] && includes != [];
  
positive.code: # often change with updating of git or cgit.
  # stripLen acts as the -p parameter when applying a patch.
  
  { lib, fetchurl, patchutils }:
  { stripLen ? 0, extraPrefix ? null, excludes ? [], includes ? [], revert ? false, ... }@args:
  
  fetchurl ({
  
negative.code:       cat "$out" 1>&2
        exit 1
      fi
      ${buildPackages.patchutils}/bin/filterdiff \
        -p1 \
        ${builtins.toString (builtins.map (x: "-x ${lib.escapeShellArg x}") excludes)} \
        ${builtins.toString (builtins.map (x: "-i ${lib.escapeShellArg x}") includes)} \
  