plugins/devkit/testData/codeInsight/pluginWithXInclude.xml

<idea-plugin version="2" xmlns:xi="http://www.w3.org/2001/XInclude">

    <id>foo</id>

    <extensionPoints>
        <extensionPoint name="bar"/>
        <xi:include href="/extensionPoints.xml" xpointer="xpointer(/extensionPoints/*)"/>
    </extensionPoints>

    <extensions defaultExtensionNs="foo">

        <bar/>
        <extension/>
    </extensions>

</idea-plugin>