What took an inordinate amount of time was not finding
<xsl:apply-imports />, but instead realizing I needed to take the namespace into account. Currently this is using the 1.76.1 stylesheets.
<xsl:stylesheet ... xmlns:d="http://docbook.org/ns/docbook" exclude-result-prefixes="d" ... > <xsl:template match="d:programlisting"> <pre><xsl:apply-imports /></pre> </xsl:template> ... </xsl:stylesheet>
d: prefix, I was scratching my head and mumbling under my breath. With the prefix, it just works.