Heroku add-ons may now be attached across applications and multiple times on a single app.
Change effective on 04 May 2015
For add-ons that are enabled to be attached, they can be attached to another application by running the command:
$ heroku addons:attach ADDON_NAME -a APP_NAME
For add-ons that are enabled to be added multiple times they can be added just as you would normally create an add-on:
$ heroku addons:create heroku-postgresql
Additionally you may now set the alias that your add-on attaches to by using the
--as flag. For example, attaching as follows sets the var
$ heroku addons:create heroku-postgresql --as API_DATABASE
Finally, the CLI now supports the use of
destroy in place of adding and removing add-ons to better align with Heroku CLI commands.