Given app/assets/javascripts/foo.js, add (or remove) the empty file
app/assets/javascripts/foo.js.coffee and the client will loop (and not
loop) the setInterval() anonymous function, as if the clearInterval()
was not called.
Also tried sprockets 2.4.4, same behaviour.
In any case, (effectively) duplicate filenames are probably not supported in sprockets.
http://stackoverflow.com/questions/8024828/sprockets-duplicate-file-naming