Shell steps for install latest drush version

download-drush.sh

cd /usr/share
sudo git clone --branch master https://github.com/drush-ops/drush.git

drush-version.sh

drush --version

install-compose.sh

curl -sS https://getcomposer.org/installer | php
mv composer.phar /usr/local/bin/composer

install-drush.sh

cd /usr/share/drush
$ sudo composer install

install-git.sh

brew install git

link-drush.sh

ln -s /usr/share/drush/drush /usr/bin/drush