Mercuial

How to use Mercurial to hack Drupal Core without killing kittens

In the Drupal community there's a paradigm that every time you hack core you kill a kitten. And who would want to kill a kittens? The point is that any time you hack core (modify the Drupal core files) it becomes a nightmare to forward-migrate your changes as Drupal core is updated. The Drupal team does routinely update Drupal (about every 2 months) and it's best to keep your Drupal installation up-to-date especially as many of the fixes are for security bugs.