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I haven't found explanation of how to upgrade this shell to 8.x for drush itself not a module using drush and the site is on Drupal 7.x site. I'm fairly new to all of this and do know how to use drush but was wondering if I should keep this shell updated. I saw there are versions 8.xx that work for Drupal 7 but didn't see instructions on updating. The version running is 8.0.x.dev so I'm guessing I should update to current 8. Version. Thanks in advance.