xslt for concatenating multiple xml files

gistfile1.xml

<!-- Option 1: Use an index XML file to list file names to be combined. Transform that XML file (root: files) with this XSL. -->
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:template match="/">
    <xml>
      <xsl:for-each select="files/file">
	<xsl:copy-of select="document(.)/xml/*"/>
      </xsl:for-each>
    </xml>
  </xsl:template>
</xsl:stylesheet>

<!-- Option 2: Name the files to be combined in the XSL -->
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:template match="/">
    <xml>
      <xsl:copy-of select="document('filename.xml')/xml/*"/>
      <!-- Use a scripting language that can manipulate XML to append child nodes here listing all the files to be combined -->
    </xml>
  </xsl:template>
</xsl:stylesheet>