> After trying to debug this problem it seems that IRB now only allows tab
> completion for the methods you get from entering "require
> 'irb/completion'", and whatever is in the folder IRB is launched from.
> So if I launch from folder "foo" which contains folder "bar", I can tab
> complete 'bar/' but won't see anything in that folder.

If you start irb without completion i.e. `irb -f`, irb should let
readline
default to file completion. You can also explicitly tell readline to
do file
completion but then you will lose irb's method completion:

   Readline.completion_proc = Readline::FILENAME_COMPLETION_PROC

If you're still having trouble with completing subdirectories, you may
need to tweak
some Readline settings: http://ruby-doc.org/core-1.9/classes/Readline.html#M003133