XSLT - Match Attributes within a group and pulling values of those attributes

I have a group of tags with attributes and I only want to pull certain values into a new group after I match attributes.

The input file looks like this:

<content>
<manifest>
<item id="id1272682" href="ch01.html"/>
<item id="id1272759" href="ch02.html"/>
</manifest>
<spine>
<itemref idref="id1272759"/>
<itemref idref="id1273380"/>
</spine>
</content>

I want my XSLT to look in the spine for any itemref/@idref values (it can be more than one) that match the item/@id in the manifest and add that value to the spine so that the output looks like this:

<spine>
<itemref idref="id1272759"/>
</spine>

Here is what I have thus far. It appears my if: statement is working as I am getting the correct amount of itemref tags but am not getting the value of the idref.

<xsl:if test="itemref[attribute::idref = ../../manifest/item/@id]">
                             <xsl:element name="itemref">
                                 <xsl:attribute name="idref">
                                     <xsl:value-of select="@id开发者_Python百科ref"/>
                                 </xsl:attribute>
                             </xsl:element>
                             </xsl:if>

And my output is:

<spine>
  <itemref idref=""/>
</spine>

This transformation:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:template match="spine">
     <spine>
       <xsl:copy-of select="itemref[@idref = /*/manifest/item/@id]"/>
     </spine>
 </xsl:template>
</xsl:stylesheet>

when applied on the provided XML document:

<content>
    <manifest>
        <item id="id1272682" href="ch01.html"/>
        <item id="id1272759" href="ch02.html"/>
    </manifest>
    <spine>
        <itemref idref="id1272759"/>
        <itemref idref="id1273380"/>
    </spine>
</content>

produces the wanted, correct result:

<spine>
   <itemref idref="id1272759"/>
</spine>