Implement part of `ssh2-generality': introduce the ability to tell

PuTTY / Plink not to run a remote shell/command at all. Supported in
the GUI configuration and via the (OpenSSH-like) -N command-line
option.

No effort is currently made to arrange `nice' UI properties. If you
do this in GUI PuTTY, a full-size terminal window will still be
created, and will sit there with almost nothing in it throughout
your session. If you do it in Plink, Plink will not accept any kind
of request to terminate gracefully; you'll have to ^C or kill it.
Nonetheless, even this little will be useful to some people...

[originally from svn r4614]

doc/config.but

@@ -1,4 +1,4 @@
-\versionid $Id: config.but,v 1.92 2004/10/06 22:31:07 jacob Exp $
+\versionid $Id: config.but,v 1.93 2004/10/13 13:43:11 simon Exp $
 
 \C{config} Configuring PuTTY
 
@@ -1936,6 +1936,27 @@ in a pseudo-terminal. In PuTTY, this is generally only useful for
 very specialist purposes; although in Plink (see \k{plink}) it is
 the usual way of working.
 
+\S{config-ssh-noshell} \q{Don't start a shell or command at all}
+
+\cfg{winhelp-topic}{ssh.noshell}
+
+If you tick this box, PuTTY will not attempt to run a shell or
+command after connecting to the remote server. You might want to use
+this option if you are only using the SSH connection for port
+forwarding, and your user account on the server does not have the
+ability to run a shell.
+
+This feature is only available in SSH protocol version 2 (since the
+version 1 protocol assumes you will always want to run a shell).
+
+This feature can also be enabled using the \c{-N} command-line
+option; see \k{using-cmdline-noshell}.
+
+If you use this feature in Plink, you will not be able to terminate
+the Plink process by any graceful means; the only way to kill it
+will be by pressing Control-C or sending a kill signal from another
+program.
+
 \S{config-ssh-comp} \q{Enable compression}
 
 \cfg{winhelp-topic}{ssh.compress}

doc/index.but

@@ -104,6 +104,7 @@ saved sessions from
 \IM{-T-upper} \c{-T} command-line option
 \IM{-t} \c{-t} command-line option
 \IM{-C-upper} \c{-C} command-line option
+\IM{-N-upper} \c{-N} command-line option
 \IM{-1} \c{-1} command-line option
 \IM{-2} \c{-2} command-line option
 \IM{-i} \c{-i} command-line option

doc/using.but

@@ -1,4 +1,4 @@
-\versionid $Id: using.but,v 1.33 2004/10/06 22:31:07 jacob Exp $
+\versionid $Id: using.but,v 1.34 2004/10/13 13:43:11 simon Exp $
 
 \C{using} Using PuTTY
 
@@ -694,6 +694,24 @@ configuration box (see \k{config-ssh-pty}).
 These options are not available in the file transfer tools PSCP and
 PSFTP.
 
+\S2{using-cmdline-noshell} \I{-N-upper}\c{-N}: suppress starting a
+shell or command
+
+The \c{-N} option prevents PuTTY from attempting to start a shell or
+command on the remote server. You might want to use this option if
+you are only using the SSH connection for port forwarding, and your
+user account on the server does not have the ability to run a shell.
+
+This feature is only available in SSH protocol version 2 (since the
+version 1 protocol assumes you will always want to run a shell).
+
+This option is equivalent to the \q{Don't start a shell or command
+at all} checkbox in the SSH panel of the PuTTY configuration box
+(see \k{config-ssh-noshell}).
+
+These options are not available in the file transfer tools PSCP and
+PSFTP.
+
 \S2{using-cmdline-compress} \I{-C-upper}\c{-C}: enable \i{compression}
 
 The \c{-C} option enables compression of the data sent across the