[XeTeX] XeTeX release notes ?

[Taylor, P]

Could anyone please tell me where I may find the release notes for XeTeX ?  I 
ask because the behaviour of \XeTeXpdffile changed somewhere between 
\XeTeXrevision = 0.99996 and \XeTeXrevision = 0.99999 (see code fragment below) 
and I would like to ensure that my code behaviour is correct for intermediate 
versions.

Philip Taylor
--------
\def \menus
    {%
        \begingroup
        \def \menufile { "Appendix D/Appendix-D.pdf" }%
        \def \doit
            {%
                \setbox 0 = \hbox {\XeTeXpdffile \menufile page \count 0 
\transformed}%
                \sb 0
            }%
        \count 0 = 1
        \loop
            \ifnum \count 0 = 10
                \ifdim \XeTeXrevision pt < 0.99999pt
                    \def \transformed {  width \vsize height \hsize rotated 90}%
                \else
                    \def \transformed {  width \hsize height \vsize}%
                \fi
            \else
                \def \transformed {  width \hsize height \vsize}%
            \fi
            \doit
        \ifnum \count 0  < \XeTeXpdfpagecount \menufile
            \advance \count 0 by 1
        \repeat
        \endgroup
    }