Improve Tramp traces.

* lisp/net/trampver.el (tramp-repository-get-version): New defun.

* lisp/net/tramp.el (tramp-debug-message): Use it.

lisp/net/tramp.el

@@ -1433,7 +1433,12 @@ ARGUMENTS to actually emit the message (if applicable)."
        (format
 	";; %sEmacs: %s Tramp: %s -*- mode: outline; -*-"
 	(if (featurep 'sxemacs) "SX" (if (featurep 'xemacs) "X" "GNU "))
-	emacs-version tramp-version)))
+	emacs-version tramp-version))
+      (when (>= tramp-verbose 10)
+	(insert
+	 (format
+	  "\n;; Location: %s Git: %s"
+	  (locate-library "tramp") (tramp-repository-get-version)))))
     (unless (bolp)
       (insert "\n"))
     ;; Timestamp.

lisp/net/trampver.el

@@ -38,6 +38,18 @@
 (defconst tramp-bug-report-address "tramp-devel@gnu.org"
   "Email address to send bug reports to.")
 
+(defun tramp-repository-get-version ()
+  "Try to return as a string the repository revision of the Tramp sources."
+  (let ((dir (funcall 'locate-dominating-file (locate-library "tramp") ".git")))
+    (when dir
+      (with-temp-buffer
+	(let ((default-directory (file-name-as-directory dir)))
+	  (and (zerop
+		(ignore-errors
+		  (call-process "git" nil '(t nil) nil "rev-parse" "HEAD")))
+	       (not (zerop (buffer-size)))
+	       (replace-regexp-in-string "\n" "" (buffer-string))))))))
+
 ;; Check for (X)Emacs version.
 (let ((x (if (or (>= emacs-major-version 22)
 		 (and (featurep 'xemacs)