Same xemacs file for different versions

[Asfand Yar Qazi]

Hi,

I need to use xemacs 21.5 and 21.4 (beta and stable) depending on
where I'm working.  I keep a darcs repository (darcs is IMHO the best
version control tool out there) of my .xemacs directory.

I need to know if it's possible to do certain customizations
differently for different versions of xemacs - is there a way of
specifying a different custom.el file for different versions to use
programatically via the init.el file, so that customize mode from
different versions don't clash, for example?

As a last resort, there has to be a variable or constant I can check
that'll give me the current version of xemacs I'm using so I can base
customizations on that.

I realise I can just use different branches for different versions,
and then synchronise shared patches between them (darcs makes that
easy) but I'd prefer a more convenient way of doing it.

Thanks