How to use Mercurial to hack Drupal Core without killing kittens

Kittens are cute and fuzzy and nobody would want to kill them, would they? Who would want to hurt that little fuzzy adorable kitten? For a couple years now I've been using the mercurial queues feature to maintain local patches to Drupal modules including Drupal core. It lets me keep local patches without having a mess when it comes time to update to newer Drupal releases, and gives me a way to communicate patches from place to place.

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