anchor.diff:    confDirs ? [],
     pluginPkgs ? [],
     localConfig ? "",
  -  shellAliases ? {}
  +  shellAliases ? {},
  +  runtimeInputs ? []
   }:
   
   let
  
positive.code:     ++ (map (vendorDir "conf") pluginPkgs)
      ++ (map (vendorDir "conf") [ localFishConfig shellAliasesFishConfig ]);
  
  in writeShellScriptBin "fish" ''
    ${fish}/bin/fish --init-command "
      set --prepend fish_complete_path ${lib.escapeShellArgs complPath}
      set --prepend fish_function_path ${lib.escapeShellArgs funcPath}
      set --local fish_conf_source_path ${lib.escapeShellArgs confPath}
      for c in \$fish_conf_source_path/*; source \$c; end
    " "$@"
  '')
  
negative.code: { lib, writeShellApplication, fish, writeTextFile }:
  
  lib.makeOverridable ({
    completionDirs ? [],
  