Use RemoteCommand option for Tramp's sshx and scpx methods

* doc/misc/tramp.texi (Inline methods) <sshx>:
(External methods) <scpx>: Adapt call sequence.
(Remote shell setup): Mention, that sshx and scpx overwrite
RemoteCommand.
(Remote processes): Restriction: direct asynchronous processes
cannot be used when RemoteCommand is in use.
`tramp-remote-process-environment' is not ignored any longer.

* lisp/net/tramp-sh.el (tramp-methods) <sshx, scpx>: Handle login
shell via RemoteCommand.  Remove `tramp-direct-async' parameter.
(tramp-maybe-open-connection): Add "-i" to login.

* lisp/net/tramp-smb.el (tramp-smb-errors):
Add "NT_STATUS_NOT_SUPPORTED".
(tramp-smb-handle-insert-directory): Fix point moving error.

* test/lisp/net/tramp-tests.el (tramp-test34-explicit-shell-file-name):
Use `get-buffer-process' where appropriate.

1 files changed, 17 insertions, 10 deletions

diff --git a/doc/misc/tramp.texi b/doc/misc/tramp.texi
index e9ffd6a8c43..5d89b065882 100644
--- a/doc/misc/tramp.texi
+++ b/doc/misc/tramp.texi
@@ -810,9 +810,10 @@ behavior.
 @cindex @option{sshx} method
 
 Works like @option{ssh} but without the extra authentication prompts.
-@option{sshx} uses @samp{ssh -t -t @var{host} -l @var{user} /bin/sh}
-to open a connection with a ``standard'' login shell.  It supports
-changing the remote login shell @command{/bin/sh}.
+@option{sshx} uses @samp{ssh -t -t -l @var{user} -o
+RemoteCommand='/bin/sh -i' @var{host}} to open a connection with a
+``standard'' login shell.  It supports changing the remote login shell
+@command{/bin/sh}.
 
 @strong{Note} that @option{sshx} does not bypass authentication
 questions.  For example, if the host key of the remote host is not
@@ -935,9 +936,10 @@ This method supports the @samp{-p} argument.
 @cindex @command{ssh} (with @option{scpx} method)
 
 @option{scpx} is useful to avoid login shell questions.  It is similar
-in performance to @option{scp}.  @option{scpx} uses @samp{ssh -t -t
-@var{host} -l @var{user} /bin/sh} to open a connection.  It supports
-changing the remote login shell @command{/bin/sh}.
+in performance to @option{scp}.  @option{scpx} uses @samp{ssh -t -t -l
+@var{user} -o RemoteCommand='/bin/sh -i' @var{host}} to open a
+connection.  It supports changing the remote login shell
+@command{/bin/sh}.
 
 @option{scpx} is useful for MS Windows users when @command{ssh}
 triggers an error about allocating a pseudo tty.  This happens due to
@@ -2220,7 +2222,10 @@ This uses also the settings in @code{tramp-sh-extra-args}.
 @vindex RemoteCommand@r{, ssh option}
 @strong{Note}: If you use an @option{ssh}-based method for connection,
 do @emph{not} set the @option{RemoteCommand} option in your
-@command{ssh} configuration, for example to @command{screen}.
+@command{ssh} configuration, for example to @command{screen}.  On the
+other hand, some @option{ssh}-based methods, like @option{sshx} or
+@option{scpx}, silently overwrite a @option{RemoteCommand} option of
+the configuration file.
 
 
 @subsection Other remote shell setup hints
@@ -3580,7 +3585,6 @@ Furthermore, this approach has the following limitations:
 It works only for connection methods defined in @file{tramp-sh.el} and
 @file{tramp-adb.el}.
 
-@vindex ControlMaster@r{, ssh option}
 @item
 It does not support interactive user authentication.  With
 @option{ssh}-based methods, this can be avoided by using a password
@@ -3588,6 +3592,10 @@ agent like @command{ssh-agent}, using public key authentication, or
 using @option{ControlMaster} options.
 
 @item
+It cannot be applied for @option{ssh}-based methods, which use the
+@option{RemoteCommand} option.
+
+@item
 It cannot be killed via @code{interrupt-process}.
 
 @item
@@ -3597,8 +3605,7 @@ It does not report the remote terminal name via @code{process-tty-name}.
 It does not set process property @code{remote-pid}.
 
 @item
-It does not use @code{tramp-remote-path} and
-@code{tramp-remote-process-environment}.
+It does not use @code{tramp-remote-path}.
 @end itemize
 
 In order to gain even more performance, it is recommended to bind