Adding a directory to $LOAD_PATH (Ruby)

Question

I have seen two commonly used techniques for adding the directory of the file currently being executed to the $LOAD_PATH (or $:). I see the advantages of doing this in case

Answer 1

I'm not too fond on the 'quick-and-dirty' way. Anyone new to Ruby will be pondering what $:. is.

I find this more obvious.

libdir = File.dirname(__FILE__)
$LOAD_PATH.unshift(libdir) unless $LOAD_PATH.include?(libdir)

Or if I care about having the full path...

libdir = File.expand_path(File.dirname(__FILE__))
$LOAD_PATH.unshift(libdir) unless $LOAD_PATH.include?(libdir)

UPDATE 2009/09/10

As of late I've been doing the following:

$:.unshift(File.expand_path(File.dirname(__FILE__))) unless
    $:.include?(File.dirname(__FILE__)) || $:.include?(File.expand_path(File.dirname(__FILE__)))

I've seen it in a whole bunch of different ruby projects while browsing GitHub.

Seems to be the convention?