In Tramp, use scp "-T" argument if available

* lisp/net/tramp-sh.el (tramp-scp-strict-file-name-checking): New defvar.
(tramp-scp-strict-file-name-checking): New defun.
(tramp-do-copy-or-rename-file-out-of-band): Use it.
(tramp-methods) <scp, scpx>: Use "%x".
(tramp-make-copy-program-file-name): Use local quoting.
(tramp-sh-handle-make-process): Don't call
`tramp-maybe-open-connection', this happens implicitly by
`tramp-send-command'.

* lisp/net/tramp.el (tramp-methods): Adapt docstring.

* test/lisp/net/tramp-tests.el (tramp-test40-special-characters)
(tramp-test40-special-characters-with-stat)
(tramp-test40-special-characters-with-perl)
(tramp-test40-special-characters-with-ls): Don't skip for
`tramp--test-windows-nt-and-scp-p'.

3 files changed, 50 insertions, 17 deletions

diff --git a/lisp/net/tramp-sh.el b/lisp/net/tramp-sh.el
index b51ba11247f..57be9ecf006 100644
--- a/lisp/net/tramp-sh.el
+++ b/lisp/net/tramp-sh.el
@@ -125,6 +125,15 @@ depends on the installed local ssh version.
 
 The string is used in `tramp-methods'.")
 
+(defvar tramp-scp-strict-file-name-checking nil
+  "Which scp strict file name checking argument to use.
+
+It is the string \"-T\" if supported by the local scp (since
+release 8.0), otherwise the string \"\".  If it is nil, it will
+be auto-detected by Tramp.
+
+The string is used in `tramp-methods'.")
+
 ;; Initialize `tramp-methods' with the supported methods.
 ;;;###tramp-autoload
 (tramp--with-startup
@@ -160,8 +169,8 @@ The string is used in `tramp-methods'.")
                 (tramp-remote-shell-login   ("-l"))
                 (tramp-remote-shell-args    ("-c"))
                 (tramp-copy-program         "scp")
-                (tramp-copy-args            (("-P" "%p") ("-p" "%k") ("-q")
-                                             ("-r") ("%c")))
+                (tramp-copy-args            (("-P" "%p") ("-p" "%k")
+                                             ("%x") ("-q") ("-r") ("%c")))
                 (tramp-copy-keep-date       t)
                 (tramp-copy-recursive       t)))
  (add-to-list 'tramp-methods
@@ -177,7 +186,7 @@ The string is used in `tramp-methods'.")
                 (tramp-remote-shell-args    ("-c"))
                 (tramp-copy-program         "scp")
                 (tramp-copy-args            (("-P" "%p") ("-p" "%k")
-                                             ("-q") ("-r") ("%c")))
+                                             ("%x") ("-q") ("-r") ("%c")))
                 (tramp-copy-keep-date       t)
                 (tramp-copy-recursive       t)))
  (add-to-list 'tramp-methods
@@ -2279,7 +2288,8 @@ The method used must be an out-of-band method."
               spec (list
                     ?h (or host "") ?u (or user "") ?p (or port "")
                     ?r listener ?c options ?k (if keep-date " " "")
-                    ?n (concat "2>" (tramp-get-remote-null-device v)))
+                    ?n (concat "2>" (tramp-get-remote-null-device v))
+                    ?x (tramp-scp-strict-file-name-checking v))
               copy-program (tramp-get-method-parameter v 'tramp-copy-program)
               copy-keep-date (tramp-get-method-parameter
                               v 'tramp-copy-keep-date)
@@ -2867,14 +2877,11 @@ alternative implementation will be used."
                              (if (symbolp coding) coding (cdr coding))))
                         (clear-visited-file-modtime)
                         (narrow-to-region (point-max) (point-max))
-                        ;; We call `tramp-maybe-open-connection', in
-                        ;; order to cleanup the prompt afterwards.
                         (catch 'suppress
-                          (tramp-maybe-open-connection v)
-                          (setq p (tramp-get-connection-process v))
                           ;; Set the pid of the remote shell.  This is
                           ;; needed when sending signals remotely.
                           (let ((pid (tramp-send-command-and-read v "echo $$")))
+                            (setq p (tramp-get-connection-process v))
                             (process-put p 'remote-pid pid)
                             (tramp-set-connection-property p "remote-pid" pid))
                           ;; `tramp-maybe-open-connection' and
@@ -4737,6 +4744,31 @@ Goes through the list `tramp-inline-compress-commands'."
                                   " -o ControlPersist=no")))))))))
       tramp-ssh-controlmaster-options)))
 
+(defun tramp-scp-strict-file-name-checking (vec)
+  "Return the strict file name checking argument of the local scp."
+  (cond
+   ;; No options to be computed.
+   ((null (assoc "%x" (tramp-get-method-parameter vec 'tramp-copy-args)))
+    "")
+
+   ;; There is already a value to be used.
+   ((stringp tramp-scp-strict-file-name-checking)
+    tramp-scp-strict-file-name-checking)
+
+   ;; Determine the options.
+   (t (setq tramp-scp-strict-file-name-checking "")
+      (let ((case-fold-search t))
+        (ignore-errors
+          (when (executable-find "scp")
+            (with-tramp-progress-reporter
+                vec 4 "Computing strict file name argument"
+              (with-temp-buffer
+                (tramp-call-process vec "scp" nil t nil "-T")
+                (goto-char (point-min))
+                (unless (search-forward-regexp "unknown option -- T" nil t)
+                  (setq tramp-scp-strict-file-name-checking "-T")))))))
+      tramp-scp-strict-file-name-checking)))
+
 (defun tramp-timeout-session (vec)
   "Close the connection VEC after a session timeout.
 If there is just some editing, retry it after 5 seconds."
@@ -5229,12 +5261,11 @@ Return ATTR."
          (directory-file-name (tramp-file-name-unquote-localname vec))))
     (when (string-match-p tramp-ipv6-regexp host)
       (setq host (format "[%s]" host)))
-    ;; This does not work yet for MS Windows scp, if there are
-    ;; characters to be quoted.  Win32 OpenSSH 7.9 is said to support
-    ;; this, see
-    ;; <https://github.com/PowerShell/Win32-OpenSSH/releases/tag/v7.9.0.0p1-Beta>
+    ;; This does not work for MS Windows scp, if there are characters
+    ;; to be quoted.  OpenSSH 8 supports disabling of strict file name
+    ;; checking in scp, we use it when available.
     (unless (string-match-p "ftp$" method)
-      (setq localname (tramp-shell-quote-argument localname)))
+      (setq localname (shell-quote-argument localname)))
     (cond
      ((tramp-get-method-parameter vec 'tramp-remote-copy-program)
       localname)
diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index 015f458a63c..741ea05ceaf 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -252,6 +252,8 @@ pair of the form (KEY VALUE).  The following KEYs are defined:
     - \"%c\" adds additional `tramp-ssh-controlmaster-options'
       options for the first hop.
     - \"%n\" expands to \"2>/dev/null\".
+    - \"%x\" is replaced by the `tramp-scp-strict-file-name-checking'
+      argument if it is supported.
 
     The existence of `tramp-login-args', combined with the
     absence of `tramp-copy-args', is an indication that the
diff --git a/test/lisp/net/tramp-tests.el b/test/lisp/net/tramp-tests.el
index 1eb0d0ec619..3a199469d6b 100644
--- a/test/lisp/net/tramp-tests.el
+++ b/test/lisp/net/tramp-tests.el
@@ -6114,7 +6114,7 @@ This requires restrictions of file name syntax."
   "Check special characters in file names."
   (skip-unless (tramp--test-enabled))
   (skip-unless (not (tramp--test-rsync-p)))
-  (skip-unless (not (tramp--test-windows-nt-and-scp-p)))
+;  (skip-unless (not (tramp--test-windows-nt-and-scp-p)))
   (skip-unless (or (tramp--test-emacs26-p) (not (tramp--test-rclone-p))))
 
   (tramp--test-special-characters))
@@ -6126,7 +6126,7 @@ Use the `stat' command."
   (skip-unless (tramp--test-enabled))
   (skip-unless (tramp--test-sh-p))
   (skip-unless (not (tramp--test-rsync-p)))
-  (skip-unless (not (tramp--test-windows-nt-and-scp-p)))
+;  (skip-unless (not (tramp--test-windows-nt-and-scp-p)))
   ;; We cannot use `tramp-test-vec', because this fails during compilation.
   (with-parsed-tramp-file-name tramp-test-temporary-file-directory nil
     (skip-unless (tramp-get-remote-stat v)))
@@ -6145,7 +6145,7 @@ Use the `perl' command."
   (skip-unless (tramp--test-enabled))
   (skip-unless (tramp--test-sh-p))
   (skip-unless (not (tramp--test-rsync-p)))
-  (skip-unless (not (tramp--test-windows-nt-and-scp-p)))
+;  (skip-unless (not (tramp--test-windows-nt-and-scp-p)))
   ;; We cannot use `tramp-test-vec', because this fails during compilation.
   (with-parsed-tramp-file-name tramp-test-temporary-file-directory nil
     (skip-unless (tramp-get-remote-perl v)))
@@ -6167,7 +6167,7 @@ Use the `ls' command."
   (skip-unless (tramp--test-enabled))
   (skip-unless (tramp--test-sh-p))
   (skip-unless (not (tramp--test-rsync-p)))
-  (skip-unless (not (tramp--test-windows-nt-and-scp-p)))
+;  (skip-unless (not (tramp--test-windows-nt-and-scp-p)))
 
   (let ((tramp-connection-properties
          (append