libpkg/metalog: escape spaces in filenames

[khorben]

Still marked as draft until I can test it properly, as I have a build issue on my system (FreeBSD 15.1-STABLE/amd64).

Sponsored by: The FreeBSD Foundation

[emaste]

I'd prefer to keep a single fprintf and handle the escaping separately, something like

p = escape_path(path);
fprintf("./%s", p...);
free(p);

Escaping only is not sufficient -- we have to escape \ also at least so that it's reversible, and also tab and some other things... from mtree's spec.c:

/*
 * vispath --
 *      strsvis(3) encodes path, which must not be longer than MAXPATHLEN
 *      characters long, and returns a pointer to a static buffer containing
 *      the result.
 */
char *
vispath(const char *path)
{
        static const char extra[] = { ' ', '\t', '\n', '\\', '#', '\0' };
        static const char extra_glob[] = { ' ', '\t', '\n', '\\', '#', '*',
            '?', '[', '\0' };
        static char pathbuf[4*MAXPATHLEN + 1];

        if (flavor == F_NETBSD6)
                strsvis(pathbuf, path, VIS_CSTYLE, extra);
        else
                strsvis(pathbuf, path, VIS_OCTAL, extra_glob);
        return pathbuf;
}

If all consumers are equally happy with VIS_CSTYLE I'd go with that, too, but that part doesn't much matter.