Clean-up read-tree error condition.

This is a follow-up to f34f2b0; list_tree() function is where it
first notices that the command line fed too many trees for us to
handle, so move the error exit message to there, and raise the
MAX_TREES to 8 (not that it matters very much in practice).

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-read-tree.c

@@ -13,16 +13,16 @@
 #include "dir.h"
 #include "builtin.h"
 
-#define MAX_TREES 4
+#define MAX_TREES 8
 static int nr_trees;
 static struct tree *trees[MAX_TREES];
 
 static int list_tree(unsigned char *sha1)
 {
 	struct tree *tree;
 
-	if (nr_trees >= 4)
-		return -1;
+	if (nr_trees >= MAX_TREES)
+		die("I cannot read more than %d trees", MAX_TREES);
 	tree = parse_tree_indirect(sha1);
 	if (!tree)
 		return -1;
@@ -264,9 +264,6 @@ int cmd_read_tree(int argc, const char **argv, const char *unused_prefix)
 			opts.head_idx = 1;
 	}
 
-	if (MAX_TREES < nr_trees)
-		die("I cannot read more than %d trees", MAX_TREES);
-
 	for (i = 0; i < nr_trees; i++) {
 		struct tree *tree = trees[i];
 		parse_tree(tree);