git-diff: fix combined diff

The code forgets that typecast binds tighter than addition, in
other words:

    (cast *)array + i  === ((cast *)array) + i

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-diff.c

@@ -192,7 +192,8 @@ static int builtin_diff_combined(struct rev_info *revs,
 	parent = xmalloc(ents * sizeof(*parent));
 	/* Again, the revs are all reverse */
 	for (i = 0; i < ents; i++)
-		hashcpy((unsigned char*)parent + i, ent[ents - 1 - i].item->sha1);
+		hashcpy((unsigned char *)(parent + i),
+			ent[ents - 1 - i].item->sha1);
 	diff_tree_combined(parent[0], parent + 1, ents - 1,
 			   revs->dense_combined_merges, revs);
 	return 0;