>> +(put 'beginning-of-buffer 'isearch-match-scroll 'isearch-beginning-of-buffer)
>> +(put 'end-of-buffer 'isearch-match-scroll 'isearch-end-of-buffer)
>> +(put 'scroll-up-command 'isearch-match-scroll 'isearch-scroll-up)
>> +(put 'scroll-down-command 'isearch-match-scroll 'isearch-scroll-down)
>> ...
>> +     ((and isearch-allow-match-scroll
>> +           (symbolp this-command)
>> +           (get this-command 'isearch-match-scroll))
>> +      (setq this-command (get this-command 'isearch-match-scroll)))
>
> As noted in another message, this is basically the same as:
>
>  (define-key isearch-mode-map [remap beginning-of-buffer] 'isearch-beginning-of-buffer)
>  (define-key isearch-mode-map [remap end-of-buffer] 'isearch-end-of-buffer)
>  (define-key isearch-mode-map [remap scroll-up-command] 'isearch-scroll-up)
>  (define-key isearch-mode-map [remap scroll-down-command] 'isearch-scroll-down)
>

I'm not sure I understand what you mean by this.  Indeed this can be done 
that way, too, but in that case it isn't a user option anymore, which can 
be easily set and toggled.

I attach an updated patch, with an improved documentation (including the 
typo spotted by Howard Melman).