The Struts 2 documentation is maintained online and posted to the Apache Struts web site on a regular basis. A snapshot of the documentation is bundled with each distribution, so that people are able to refer to the documentation for that distribution.
The online version represents the latest development version ("nightly build") and may document features not available in your release. See the documentation bundled with each distribution for the best information about the features available in that distribution.
The mechanism we use to integrate is wiki snapshot with the website distribution is covered by a JIRA ticket.
The HTML version of the documentation is maintained using the AutoExport plugin. (JAR annexed.)