The usual way to get whole directories from github via a command line is with subversion.
(example)
  svn export https://github.com/ccrma/music220a/trunk/webChuck/auditory-streaming-illusion hw2

If no svn command exists on your machine and it can't be installed, here's a workaround for getting whole directories from github by running the same subversion command at CCRMA.

Be aware that this extra first step copies to wherever you'd like (in your CCRMA home directory) but that should not be your CCRMA homework factory directory (which is reserved for finished work).

1) copy from github to ccrma working directory, say ~/220a/
  login to your CCRMA account and cd to where you'd like it to go
  cd 220a
  svn export https://github.com/ccrma/music220a/trunk/webchuck/auditory-streaming hw2

2) copy the new directory from CCRMA to your own local machine's working directory
open a terminal on your machine and cd to where you'd like it to go, say 220a/
  cd 220a
  scp -r USERNAME@ccrma-gate.stanford.edu:220a/hw2 .
The above command requires substituting your CCRMA USERNAME (if your username is the same locally then you can elide `USERNAME@`

Now your own local machine has the same new directory as the original command at the top would have produced.