Best Practices for 'changing' config files?

System

DevNetters -
We've got a couple of file types that need a different version for each environment that they are deployed to, and we're looking for some advice on how to best handle them in a TeamSite / OpenDeploy environment.

For example:
There's a file named config.xml. This config.xml file needs to be deployed with each update of a particular site's contents. The config.xml file needs to be tailored specifically for each environment that an update is applied to. So if we move through a DEV > QA > STAGING > PROD update life cycle, that's 4 different version of config.xml.

Some options to handle this are:
- Keep a version of config.xml for each potential environment and attach all the needed versions of the file to a workflow and have the workflow / deployment process somehow deploy the correct version per environment.
- Keep a single version of config.xml and somewhere else keep the environment-specific info needed for config.xml. Once again, have the workflow / deployment process modify the config.xml file per environment.
- Other?? need your input here.

It should be noted that we don't always know the deployment target(s) for the assets at the time a workflow is instantiated.

And it would be optimal if we can come up with a more 'framework' generic solution here rather than coding to each occurrence that arises.

Experiences? Advice? Dig deep. All responses are much appreciated!

Wally Box
Nike, Inc.