Fix Bug#22145

* lisp/net/tramp-cache.el (tramp-get-connection-property)
(tramp-set-connection-property, tramp-connection-property-p)
(tramp-flush-connection-property): Improve docstring.

* lisp/net/tramp-sh.el (tramp-maybe-open-connection): Use it.

* lisp/net/tramp.el (tramp-get-local-locale): New defun.

* test/automated/tramp-tests.el (tramp--test-utf8):
Improve settings of coding systems.  (Bug#22145)

lisp/net/tramp-cache.el

@@ -223,8 +223,10 @@ This is suppressed for temporary buffers."
 ;;;###tramp-autoload
 (defun tramp-get-connection-property (key property default)
   "Get the named PROPERTY for the connection.
-KEY identifies the connection, it is either a process or a vector.
-If the value is not set for the connection, returns DEFAULT."
+KEY identifies the connection, it is either a process or a
+vector.  A special case is nil, which is used to cache connection
+properties of the local machine.  If the value is not set for the
+connection, returns DEFAULT."
   ;; Unify key by removing localname and hop from vector.  Work with a
   ;; copy in order to avoid side effects.
   (when (vectorp key)
@@ -241,8 +243,10 @@ If the value is not set for the connection, returns DEFAULT."
 ;;;###tramp-autoload
 (defun tramp-set-connection-property (key property value)
   "Set the named PROPERTY of a connection to VALUE.
-KEY identifies the connection, it is either a process or a vector.
-PROPERTY is set persistent when KEY is a vector."
+KEY identifies the connection, it is either a process or a
+vector.  A special case is nil, which is used to cache connection
+properties of the local machine.  PROPERTY is set persistent when
+KEY is a vector."
   ;; Unify key by removing localname and hop from vector.  Work with a
   ;; copy in order to avoid side effects.
   (when (vectorp key)
@@ -258,13 +262,17 @@ PROPERTY is set persistent when KEY is a vector."
 ;;;###tramp-autoload
 (defun tramp-connection-property-p (key property)
   "Check whether named PROPERTY of a connection is defined.
-KEY identifies the connection, it is either a process or a vector."
+KEY identifies the connection, it is either a process or a
+vector.  A special case is nil, which is used to cache connection
+properties of the local machine."
   (not (eq (tramp-get-connection-property key property 'undef) 'undef)))
 
 ;;;###tramp-autoload
 (defun tramp-flush-connection-property (key)
   "Remove all properties identified by KEY.
-KEY identifies the connection, it is either a process or a vector."
+KEY identifies the connection, it is either a process or a
+vector.  A special case is nil, which is used to cache connection
+properties of the local machine."
   ;; Unify key by removing localname and hop from vector.  Work with a
   ;; copy in order to avoid side effects.
   (when (vectorp key)

lisp/net/tramp-sh.el

@@ -4773,7 +4773,7 @@ connection if a previous connection has died for some reason."
 	      (when (and p (processp p))
 		(delete-process p))
 	      (setenv "TERM" tramp-terminal-type)
-	      (setenv "LC_ALL" "en_US.utf8")
+	      (setenv "LC_ALL" (tramp-get-local-locale vec))
 	      (if (stringp tramp-histfile-override)
 		  (setenv "HISTFILE" tramp-histfile-override)
 		(if tramp-histfile-override

lisp/net/tramp.el

@@ -3747,6 +3747,26 @@ This is used internally by `tramp-file-mode-from-int'."
       (tramp-compat-funcall 'group-gid)
     (nth 3 (file-attributes "~/" id-format))))
 
+(defun tramp-get-local-locale (&optional vec)
+  ;; We use key nil for local connection properties.
+  (with-tramp-connection-property nil "locale"
+    (let ((candidates '("en_US.utf8" "C.utf8" "en_US.UTF-8"))
+	  locale)
+      (with-temp-buffer
+	(unless (or (memq system-type '(windows-nt))
+                    (not (zerop (tramp-call-process
+                                 nil "locale" nil t nil "-a"))))
+	  (while candidates
+	    (goto-char (point-min))
+	    (if (string-match (format "^%s\r?$" (regexp-quote (car candidates)))
+			      (buffer-string))
+		(setq locale (car candidates)
+		      candidates nil)
+	      (setq candidates (cdr candidates))))))
+      ;; Return value.
+      (when vec (tramp-message vec 7 "locale %s" (or locale "C")))
+      (or locale "C"))))
+
 ;;;###tramp-autoload
 (defun tramp-check-cached-permissions (vec access)
   "Check `file-attributes' caches for VEC.

test/lisp/net/tramp-tests.el

@@ -2033,9 +2033,12 @@ Use the `ls' command."
 
 (defun tramp--test-utf8 ()
   "Perform the test in `tramp-test32-utf8*'."
-  (let ((coding-system-for-read 'utf-8)
-	(coding-system-for-write 'utf-8)
-	(file-name-coding-system 'utf-8))
+  (let* ((utf8 (if (and (eq system-type 'darwin)
+			(memq 'utf-8-hfs (coding-system-list)))
+		   'utf-8-hfs 'utf-8))
+	 (coding-system-for-read utf8)
+	 (coding-system-for-write utf8)
+	 (file-name-coding-system utf8))
     (tramp--test-check-files
      (unless (tramp--test-hpux-p) "Γυρίστε το Γαλαξία με Ώτο Στοπ")
      (unless (tramp--test-hpux-p)