(minibuffer-default-add-function): New variable with

(minibuffer-default-add-function): New variable with
the default to minibuffer-default-add-completions.
(minibuffer-default-add-done): New variable.  Make it buffer-local.
(minibuffer-default-add-completions): New function.
(goto-history-element): Set minibuffer-default-add-done to t and
call a function in minibuffer-default-add-function when the
specified absolute history position is greater than the length of
the minibuffer-default list and minibuffer-default-add-done is nil.
Change "^End of history; no next item$" to "^End of defaults;
no next item$".