[TxMt] Pointing TM's ri / rdoc lookup at a non-standard directory

[Robert Poor]

Disclaimer: I've been playing with TM for about 30 minutes, i.e. I'm a  
complete newcomer.  One of the main reasons I'm considering abandoning  
my beloved emacs in favor of TM is the integrated ri / documentation  
lookup.  But I haven't been able to get that to work.

Briefly, my question is: how can I get the TM help system to use  
ruby / rails documentation from a sandboxed directory?

Some details:

In my development machine I have carefully built versions of ruby  
1.9.1, rails, ri, rdoc, all of my gems, etc in a sandboxed directory  
(~/Development/Ruby/bin/*), and I've left the Mac OS X standard  
distributions alone.

If I try to use TM's ^h help lookup, I get a message like:

/Applications/TextMate.app/Contents/SharedSupport/Bundles/ 
Ruby.tmbundle/Support/bin/linked_ri.rb:13: command not found: ri -T -f  
plain belongs_to

... presumably since it can't find 'ri'.  Digging in, I can ask TM to  
tell me more about its environment:

which ri^r =>
/opt/local/bin/ri

ls -l /opt/local/bin/ri^r =>
-rwxr-xr-x  2 root  admin  1491 Aug  5  2009 /opt/local/bin/ri

echo $PATH^r =>
/Applications/TextMate.app/Contents/SharedSupport/Support/bin/ 
CocoaDialog.app/Contents/MacOS:/usr/local/git/bin:/opt/local/bin:/opt/ 
local/sbin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/X11/bin:/ 
Applications/TextMate.app/Contents/SharedSupport/Support/bin

(Another disclaimer: I'm also new to ri / rdoc, so this may ultimately  
be an ri / rdoc question rather than a TM question.)

- rdp