git-show-branch: Fix off-by-one error.

Signed-off-by: Junio C Hamano <junkio@cox.net>

show-branch.c

@@ -247,7 +247,7 @@ static int append_ref(const char *refname, const unsigned char *sha1)
 	struct commit *commit = lookup_commit_reference_gently(sha1, 1);
 	if (!commit)
 		return 0;
-	if (MAX_REVS < ref_name_cnt) {
+	if (MAX_REVS <= ref_name_cnt) {
 		fprintf(stderr, "warning: ignoring %s; "
 			"cannot handle more than %d refs",
 			refname, MAX_REVS);