Two days ago Drush team announced the release of Drush 6.
They moved there codebase to git now.
If you are drupal developer then you know the importance of drush. This is the bigest news for drupal developers.
Drush 6 relase and added support for drupal 8 version
Note: if you are using Drupal 8, you should stick with a frequently updated clone of master branch. Drush 6 supports Drupal 6+7 but not Drupal 8.
If you are using the linux then you can use following commands for updating the drush installation on your box.
Here I am assuming you already installed the drush on your linux box.
# pear install drush/drush-6.0.0RC4
# pear upgrade drush/drush
If you did not installed the drush then you can use the following link for drush installation.