master 28bf387: Tweak Fdirectory_append for efficiency

[Eli Zaretskii]

> --- a/src/fileio.c
> +++ b/src/fileio.c
> @@ -795,7 +795,8 @@ usage: (record DIRECTORY &rest COMPONENTS) */)
>        for (i = 0; i < nargs; i++)
>       {
>         Lisp_Object arg = args[i];
> -       if (STRING_MULTIBYTE (arg))
> +       /* Use multibyte or all-ASCII strings as is. */
> +       if (STRING_MULTIBYTE (arg) || SCHARS (arg) == SBYTES (arg))
>           elements[i] = arg;
>         else
>           elements[i] = make_multibyte_string (SSDATA (arg), SCHARS (arg),
> 

Isn't SCHARS (arg) == SBYTES (arg) true for any unibyte string, even
one that includes non-ASCII characters?