   "Retrieve the list of files modified by COMMIT."
   (let (files)
     (with-temp-buffer
-      (git-call-process t "diff-tree" "-m" "-r" "-z" "--name-only" "--no-commit-id" commit)
+      (git-call-process t "diff-tree" "-m" "-r" "-z" "--name-only" "--no-commit-id" "--root" commit)
       (goto-char (point-min))
       (while (re-search-forward "\\([^\0]*\\)\0" nil t 1)
         (push (match-string 1) files)))

  (when (git-empty-db-p) (error "No commit to amend."))
  (let* ((commit (git-rev-parse "HEAD"))
         (files (git-get-commit-files commit)))
    (when (git-call-process-display-error "reset" "--soft" "HEAD^")
      (git-update-status-files (copy-sequence files) 'uptodate)
      (git-mark-files git-status files)
      (git-refresh-files)

(defun git-update-ref (ref newval &optional oldval reason)
  "Update a reference by calling git-update-ref."
  (let ((args (and oldval (list oldval))))
    (when newval (push newval args))
    (push ref args)
    (when reason
     (push reason args)
     (push "-m" args))
    (unless newval (push "-d" args))
    (apply 'git-call-process-display-error "update-ref" args)))

(defun git-read-tree (tree &optional index-file)
