Add <mirrorOf>*</mirrorOf> feature

After a recent email to Maven Users list, I discovered the new <mirrorOf>*</mirrorOf> feature has not been documented anywhere official.

It is not in the 2.0.5 changelog, nor in JIRA (that I've found), nor in settings.xml reference [1], etc. The only place this has been "documented" is on the Maven Users and Maven Developer email lists, and in various blogs [2]. I find it very strange that a new feature made it into Maven without a corresponding JIRA – so perhaps it might even make sense to retroactively add it?

This needs to be documented somewhere (probably multiple places) asap.

[1] http://maven.apache.org/ref/2.0.4/maven-settings/settings.html#class_mirror
[2] http://jroller.com/page/carlossg?entry=proxying_and_hosting_a_maven