zlib: properly clamp to uLong

On platforms where `unsigned long` and `size_t` differ in bit size, we
want to clamp the buffers we pass to zlib to the former's size, as per
d05d666 (git-zlib: handle data streams larger than 4GB, 2026-05-08).

The logic introduced in that commit performs a clamping to the bits,
though, which fails to do what is needed here: If too many bytes are
available in the buffers, we need to clamp to the maximum value of an
`unsigned long`. Otherwise, we ask zlib to use too small buffers, in the
worst case using 0 as the size (think: a value whose 32 lowest bits are
all zero).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

git-zlib.c

@@ -42,8 +42,10 @@ static void zlib_pre_call(git_zstream *s)
 {
 	s->z.next_in = s->next_in;
 	s->z.next_out = s->next_out;
-	s->z.total_in = (uLong)(s->total_in & ULONG_MAX_VALUE);
-	s->z.total_out = (uLong)(s->total_out & ULONG_MAX_VALUE);
+	s->z.total_in = (uLong)(s->total_in < ULONG_MAX_VALUE ?
+		s->total_in : ULONG_MAX_VALUE);
+	s->z.total_out = (uLong)(s->total_out < ULONG_MAX_VALUE ?
+		s->total_out : ULONG_MAX_VALUE);
 	s->z.avail_in = zlib_buf_cap(s->avail_in);
 	s->z.avail_out = zlib_buf_cap(s->avail_out);
 }