clone: detect and fail on excess parameters

"git clone [options] $src $dst excess-garbage" simply ignored
excess-garbage without giving any diagnostic message.  Fix it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-clone.sh

@@ -219,6 +219,7 @@ fi
 if test -n "$2"
 then
 	dir="$2"
+	test $# == 2 || die "excess parameter to git-clone"
 else
 	# Derive one from the repository name
 	# Try using "humanish" part of source repo if user didn't specify one

t/t5601-clone.sh

@@ -0,0 +1,26 @@
+#!/bin/sh
+
+test_description=clone
+
+. ./test-lib.sh
+
+test_expect_success setup '
+
+	rm -fr .git &&
+	test_create_repo src &&
+	(
+		cd src
+		>file
+		git add file
+		git commit -m initial
+	)
+
+'
+
+test_expect_success 'clone with excess parameters' '
+
+	test_must_fail git clone -n "file://$(pwd)/src" dst junk
+
+'
+
+test_done