* net/tramp.el (tramp-ssh-controlmaster-template): Make it a

defconst.  Apply independent check for ControlPersist.

2 files changed, 16 insertions, 5 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 9ecf7ebddd7..4210740791f 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,8 @@
 2013-02-21  Michael Albinus  <michael.albinus@gmx.de>
 
+        * net/tramp.el (tramp-ssh-controlmaster-template): Make it a
+        defconst.  Apply independent check for ControlPersist.
+
         * net/tramp-sh.el (tramp-sh-handle-set-file-times): Set $UTC only
         temporarily, via "env".
 
diff --git a/lisp/net/tramp.el b/lisp/net/tramp.el
index 89648b0e9a9..5305484e920 100644
--- a/lisp/net/tramp.el
+++ b/lisp/net/tramp.el
@@ -281,16 +281,24 @@ started on the local host.  You should specify a remote host
 useful only in combination with `tramp-default-proxies-alist'.")
 
 ;;;###tramp-autoload
-(defvar tramp-ssh-controlmaster-template
+(defconst tramp-ssh-controlmaster-template
+  (let (result)
     (ignore-errors
       (with-temp-buffer
         (call-process "ssh" nil t nil "-o" "ControlMaster")
         (goto-char (point-min))
         (when (search-forward-regexp "Missing ControlMaster argument" nil t)
-          '("-o" "ControlPath=%t.%%r@%%h:%%p"
-            "-o" "ControlMaster=auto"
-            "-o" "ControlPersist=no"))))
-    "Call ssh to detect whether it supports the ControlMaster argument.
+          (setq result
+                '("-o" "ControlPath=%t.%%r@%%h:%%p"
+                  "-o" "ControlMaster=auto"))))
+      (when result
+        (with-temp-buffer
+          (call-process "ssh" nil t nil "-o" "ControlPersist")
+          (goto-char (point-min))
+          (when (search-forward-regexp "Missing ControlPersist argument" nil t)
+            (setq result (append result '("-o" "ControlPersist=no")))))))
+    result)
+    "Call ssh to detect whether it supports the Control* arguments.
 Return a template to be used in `tramp-methods'.")
 
 (defcustom tramp-default-method