file1.xml
<config>
<state version="10">
<root value="100" group="5">
<leaf number = "2"/>
</root>
<root value="101" group="6">
<leaf number = "3"/>
</root>
</state>
</config>
file2.xml
<config>
<state version="10">
<root value="100" group="5">
<leaf number = "6"/>
</root>
<root value="101" group="6">
<leaf number = "4"/>
</root>
</state>
</config>
output.xml
<config>
<state version="10">
<root value="100" group="5">
<leaf number = "2"/>
<leaf number = "6"/>
</root>
<root value="101" group="6">
<leaf number = "3"/>
<leaf number = "4"/>
</root>
</state>
</config>
I tried writing an XSLT based on the answer here: How to merge 2 XML files with common nodes using XSLT?
but I do not know how to compare based on attribute values (in this case, attributes value and group of 'root' tag? Can someone please help?