This is basically aimed at generalizing <foo>-env.sh. It can be used for having a single client for multiple clusters or anything else where you might want to have a system-level defaults and then
user-level ones. It is NOT explicitly for *xml. It is a replacement/augmentation for *env.sh
The trouble with the current Hadoop ecosystem is that it is very developer-centric in its use of <foo>-env.sh:
- this script must come from the HOME of the component and not system-level location
- this script doesn't allow for a second level of defaults
Essentially, if you want to override things in, lets say, hadoop-env.sh you can only do it at a system-level leaving the user to use .bashrc for user-level overrides. That's the core issue this JIRA is trying to address.