add usage message when too few args

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@36679 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/Main.java

@@ -63,10 +63,14 @@ public class Main {
 
     public static int run(String[] args) throws Exception {
         String home = getHudsonHome();
-        if(home==null) {
+        if (home==null) {
             System.err.println("HUDSON_HOME is not set.");
             return -1;
         }
+        if (args.length < 2) {
+            System.err.println("Usage: <job-name> <command> <args..>");
+            return -1;
+        }
 
         return remotePost(args);
     }