Dmitry Gutov <dgutov@yandex.ru> writes:

> Alternatively, one regexp would have to handle both versions, with and
> without null (merging grep-with-null-regexp-alist and
> grep-fallback-regexp-alist together, if it's at all possible).

It is possible, the regexp gets a bit more complicated and the
without-null case can now become confused by files containing NUL bytes,
but that's probably fairly rare and things do get simpler again for
callers.  Seems like the best solution overall.