magento/magento2 — pull request #41 by Vinai (2012-07-11 13:57:13+00:00)
Title: Environment based local.xml merging

Support merging an additional local.xml file based on the value of
the MAGE_APPLICATION_ENV environment variable.
The name of the file will be built as follows:

'app/etc/local.' . $_SERVER['MAGE_APPLICATION_ENV'] . '.xml'

The value of the variable is checked to contain only letters,
characters, underscores and dashes.
The file will be merged after the regular local.xml file.

The background idea is described by Matthias Zeis at
https://github.com/magento/magento2/issues/7