I don't use this file myself, but this looks like it won't Just Work on OS X and if bash_completion isn't installed (looking at https://github.com/jweslley/rails_completion/issues/2). My uninformed opinion is that completion that works in most places on most systems is probably better than completion that works in all places on fewer systems (?)

@sorbits @RedX2501 @curinir You touched this file before, do you have an opinion on this?