convert "oidcmp() != 0" to "!oideq()"

This is the flip side of the previous two patches: checking
for a non-zero oidcmp() can be more strictly expressed as
inequality. Like those patches, we write "!= 0" in the
coccinelle transformation, which covers by isomorphism the
more common:

  if (oidcmp(E1, E2))

As with the previous two patches, this patch can be achieved
almost entirely by running "make coccicheck"; the only
differences are manual line-wrap fixes to match the original
code.

There is one thing to note for anybody replicating this,
though: coccinelle 1.0.4 seems to miss the case in
builtin/tag.c, even though it's basically the same as all
the others. Running with 1.0.7 does catch this, so
presumably it's just a coccinelle bug that was fixed in the
interim.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

fetch-pack.c

@@ -599,7 +599,7 @@ static void filter_refs(struct fetch_pack_args *args,
 			continue;
 		if (parse_oid_hex(ref->name, &oid, &p) ||
 		    *p != '\0' ||
-		    oidcmp(&oid, &ref->old_oid))
+		    !oideq(&oid, &ref->old_oid))
 			continue;
 
 		if ((allow_unadvertised_object_request &