ruby versions api compatability

[Mohammed Morsi]

Hey Jeroen, thanks alot for your Ruby roundtable discussion at FUDCon. I 
was looking around for various solutions to the Ruby version 
compatibility problem for Fedora/Yum and recalled the 'alternatives' 
utility which I believe might help out w/ this problem as well.

It is shipped as part of the 'chkconfig' package so it's pretty standard 
on Fedora, and was (according to the manpage) originally written for 
this same problem w/ Perl.

http://linux.about.com/library/cmd/blcmdl8_alternatives.htm

I recall using it a while back to install various various of Java side 
by side in a single environment (pretty good overview here 
http://lanestechblog.blogspot.com/2008/03/using-alternatives-in-linux-to-use.html).

I could see this being useful if we wanted to support installing many 
different versions of the Ruby interpreter or different Ruby 
interpreters entirely side by side on a single system.

One thing I'm not currently sure of is how we would handle the different 
ruby lib and gem paths depending on which alternative is setup. If we 
can swap in the correct lib / gem path depending on which alternative is 
selected (systemwide or by the user) we should be good.

Any thoughts on this? It might be a little more complicated than doing 
the different vendor/version site dirs alone but might provide a nice 
way for multiple version support.

     -Mo