This will be used by the Timestamper plugin to insert a timestamp on each line of the BuildListener output. (Currently it modifies the launcher output instead, which can have unwanted side-effects such as JENKINS-7111.)

Preferred Approach (JENKINS-7112_decorateLogger.patch)
Add a decorateLogger method to the BuildWrapper class, which can be optionally overridden to wrap the BuildListener's default logger.

Alternate Approach (JENKINS-7112.patch)
Add a decorateBuildListener method to the BuildWrapper class, which can be optionally overridden to wrap the default BuildListener. I have decided to not use this approach, since:

• Other than wrapping the logger, it doesn't seem useful for plugins to alter the behaviour of the BuildListener.
• It would make it more difficult to evolve the BuildListener interface in future.

Both patches were created from the directory:
https://hudson.dev.java.net/svn/hudson/trunk/hudson/main/core/

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