I put all source in to lib/ path, and named a lib/foo path for my foo
project.  However, is there a better approach to require the ruby
source which in lib/foo/ from the file in the same path.

For example, lib/foo/db.rb require lib/foo/configure.rb, currently I
write:
require "#{File.dirname(__FILE__)}/../configure"

But it is a ugly way to require other files. Would anyone explain a
more "standard" approach to do it?