Use lisp cd function to change directories to avoid shell dependencies

This fixes git version determination on windows for cygwin and for msysGit
where git is installed in the user's PATH for the windows command shell.

lisp/org.el

@@ -104,25 +104,27 @@ With prefix arg HERE, insert it at point."
   (interactive "P")
   (let* ((org-version org-version)
 	 (git-version)
-	 (dir (concat (file-name-directory (locate-library "org")) "../" )))
+	 (dir (concat (file-name-directory (locate-library "org")) "../" ))
+	 (version))
     (if (file-exists-p (expand-file-name ".git" dir))
-	(progn
-	 (shell-command (concat "cd " dir " && git describe --abbrev=4 HEAD"))
-	 (save-excursion
-	   (set-buffer "*Shell Command Output*")
-	   (goto-char (point-min))
-	   (replace-regexp "-" ".")
-	   (goto-char (point-min))
-	   (re-search-forward "[^\n]+")
-	   (setq git-version (match-string 0))
-	   (shell-command (concat "cd " dir " && git diff-index --name-only HEAD --"))
-	   (unless (eql 1 (point-max))
-	     (setq git-version (concat git-version ".dirty")))
-	   (setq org-version (concat org-version " (" git-version ")")))))
-    (let ((version (format "Org-mode version %s" org-version)))
-      (if here (insert version))
-      (message version)
-      version)))
+	(let ((pwd (substring (pwd) 10)))
+	  (cd dir)
+	  (shell-command "git describe --abbrev=4 HEAD")
+	  (save-excursion
+	    (set-buffer "*Shell Command Output*")
+	    (goto-char (point-min))
+	    (re-search-forward "[^\n]+")
+	    (setq git-version (match-string 0))
+	    (subst-char-in-string ?- ?. git-version t)
+	    (shell-command "git diff-index --name-only HEAD --")
+	    (unless (eql 1 (point-max))
+	      (setq git-version (concat git-version ".dirty")))
+	    (setq org-version (concat org-version " (" git-version ")")))
+	  (cd pwd)))
+    (setq version (format "Org-mode version %s" org-version))
+    (if here (insert version))
+    (message version)
+    version))
 
 ;;; Compatibility constants