Adds Drush 6 formula for stable beta release

Library/Formula/drush-6.rb

@@ -0,0 +1,16 @@
+require 'formula'
+
+class Drush6 < Formula
+  homepage 'http://drupal.org/project/drush'
+  url 'http://ftp.drupal.org/files/projects/drush-8.x-6.0-beta1.tar.gz'
+  sha1 'e7f24717a3b4d5e07df7a9708ff0540f8aae2968'
+
+  # 8.x-6.0-beta1 (http://drupalcode.org/project/drush.git/tree/77328df783d36aa2cf74b4fcb4ee90ae7ff21994)
+  head 'git://git.drupal.org/project/drush.git', :tag => '8.x-6.0-beta1'
+
+  def install
+    libexec.install Dir['*']
+    bin.install_symlink "#{libexec}/drush" => "drush6"
+    system "ln -s #{bin}/drush6 #{HOMEBREW_PREFIX}/bin/drush6"
+  end
+end