User selectable prediction mode (fixes #9 github issue)

scripts/mosh

@@ -26,16 +26,31 @@ $|=1;
 
 my $client = 'mosh-client';
 my $server = 'mosh-server';
+my $predict = 'adaptive';
 
 my $usage =
 qq{Usage: $0 [options] [user@]host
-   --client=PATH        mosh client on local machine  (default: "mosh-client")
-   --server=PATH        mosh server on remote machine (default: "mosh-server")\n};
+    --client=PATH        mosh client on local machine  (default: "mosh-client")
+    --server=PATH        mosh server on remote machine (default: "mosh-server")
+
+    --predict=adaptive   local echo for slower links [default]
+-a  --predict=always     use local echo even on fast links
+-n  --predict=never      never use local echo
+
+Please report bugs to mosh-devel\@mit.edu.
+Mosh home page: http://mosh.mit.edu\n};
 
 GetOptions( 'client=s' => \$client,
 	    'server=s' => \$server,
+	    'predict=s' => \$predict,
+	    'a' => sub { $predict = 'always' },
+	    'n' => sub { $predict = 'never' },
 	    'fake-proxy!' => \my $fake_proxy ) or die $usage;
 
+if ( not exists { adaptive => 0, always => 0, never => 0 }->{ $predict } ) {
+  die $usage;
+}
+
 if ( defined $fake_proxy ) {
   use Errno qw(EINTR);
   use IO::Socket::INET;
@@ -122,5 +137,5 @@ if ( $pid == 0 ) { # child
 
   # Now start real mosh client
   $ENV{ 'MOSH_KEY' } = $key;
-  exec {$client} ($client, $ip, $port);
+  exec {$client} ($client, $ip, $port, $predict);
 }