git clone https://github.com/achamian/emacs.d.git ~/.emacs.d

brew install texinfo && brew link texinfo --force

cat <<EOF > /usr/local/bin/em
#!/usr/bin/env sh
if [ -z \$1 ]; then
  LAUNCH_DIR=\$PWD
else
  LAUNCH_DIR=\$1
fi
open -n -a Emacs \$LAUNCH_DIR
EOF
chmod 755 /usr/local/bin/em

Now from any directory you can run em to start emacs in that dir or run em /path/to/dir to open a particular directory