Change owner/permissions in document root for OSX.

# change group
$ sudo chgrp -R _www ~/www/sf/var
# change write permissions
$ chmod -R go+w ~/www/sf/var

Jenkins + Github auth with keys.

Generate keys on Jenkins server (without passphrase):

$ ssh-keygen

Try to connect Github via ssh:

$ ssh -T git@github.com
The authenticity of host 'github.com (207.97.227.239)' can't be established.
RSA key fingerprint is 16:27:ac:a5:76:28:2d:36:63:1b:56:4d:eb:df:a6:48.
Are you sure you want to continue connecting (yes/no)? yes
Hi username/reponame! You've successfully authenticated, but GitHub does not provide shell access.

Notice that you're asked to allow github's hostname to be added to your known_hosts file: without completing this step, you're doomed. Use Git protocol link in Jenkins config:

git@github.com:username/reponame.git