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>

tree-diff.c

@@ -491,7 +491,7 @@ static struct combine_diff_path *ll_diff_tree_paths(
 						continue;
 
 					/* diff(t,pi) != ø */
-					if (oidcmp(t.entry.oid, tp[i].entry.oid) ||
+					if (!oideq(t.entry.oid, tp[i].entry.oid) ||
 					    (t.entry.mode != tp[i].entry.mode))
 						continue;