+(defun git-get-top-dir (dir)
+ "Retrieve the top-level directory of a git tree."
+ (let ((cdup (with-output-to-string
+ (with-current-buffer standard-output
+ (cd dir)
+ (unless (eq 0 (call-process "git" nil t nil
+ "rev-parse" "--show-cdup"))
+ (error "cannot find top-level git tree for %s." dir))))))
+ (expand-file-name (concat (file-name-as-directory dir)
+ (car (split-string cdup "\n"))))))
+