Maintaining different settings on different environments with Drush

On nearly every site I have ever worked on there has been one or two settings that I wanted set differently on dev as compared to prod. Of course I could just set the settings locally, however every time I would bring the production database down those settings would be overridden. For example I always want to have the devel module enabled locallay to —ya know— help me devel, but I amost never want it enabled on production. To solve this problem I've written a simple Drush command called "environmnet." Here's how it works…

Installing is easy…

• First things first, follow these instructions to clone the Drupal sandbox project so that the environment.drush.inc file lives in your sites/all/drush folder. What's that, you don't HAVE a sites/all/drush folder!? Now's the time to make one.
• Next, open (or create) sites/all/drush/drushrc.php and add the following code (modify to taste):

// Add this to your drushrc file and modify as needed.
// The option key MUST be enviroments.
$options['environments'] = array(
  // #key = The enviroment name.
  'dev' => array(
    // The list of modules to enabled (1) or disable (0).
    'modules' => array(
      'views_ui' => 1,
      'devel' => 1,
      'memcache' => 0,
    ),
    // The list of variables to configure.
    'settings' => array(
      'preprocess_css' => 0,
      'preprocess_js' => 0,
    ),
    // The list of roles to grant (1) and revoke (0) on a per role basis.
    'permissions' => array(
      'Administrator' => array (
        'administer permissions' => 1,
      ),
      'anonymous user' => array (
        'administer permissions' => 1,
      )
    ),
  ),

  'prod' => array(
    // The list of modules to enabled (1) or disable (0).
    'modules' => array(
      'views_ui' => 0,
      'devel' => 0,
      'memcache' => 1,
    ),
    // The list of variables to configure.
    'settings' => array(
      'preprocess_css' => 0,
      'preprocess_js' => 0,
    ),
    // The list of roles to grant (1) and revoke (0) on a per role basis.
    'permissions' => array(
      'Administrator' => array (
        'administer permissions' => 1,
      ),
      'anonymous user' => array (
        'administer permissions' => 0,
      )
    ),
  ),
);

...and that's it. Well, almost. Now we have to run the command:

drush environment prod

Running this command (based on the example code above) will disable the views_ui & devel modules; enable the memcache module; turn on preprocess_css & preprocess_js by setting those variables; and turning on/off the "administer permissions" for different roles.

Alternatively, give this command a try:

drush environment dev

...and you'll see that (based on the example code above) the views_ui & devel modules will be enabled; the memcache module will be disabled; preprocess_css & preprocess_js is disabled; "administer permissions" is turned off/on for different roles.

Suggestions welcome.