Use "=" instead of "==" in condition as it is more portable

At least the dash from Ubuntu's /bin/sh says:

    test: 233: ==: unexpected operator

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-clone.sh

@@ -219,7 +219,7 @@ fi
 if test -n "$2"
 then
 	dir="$2"
-	test $# == 2 || die "excess parameter to git-clone"
+	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