Merge entries in XML with XSLT

Here is a snippet from my XML file, every product is an individual <SHOPITEM> :

<?xml version="1.0" encoding="UTF-8"?>
<SHOP>
    <SHOPITEM>
        <CATEGORY>Full</CATEGORY>
        <WHEEL>27.5</WHEEL>
        <FRAMESIZE>MD</FRAMESIZE>
        <CODE>032,00</CODE>
        <PRODUCT>POINT</PRODUCT>
        <COLOR>black / white</COLOR>
        <NOTE>Available 15.2.2015</NOTE>
        <URL></URL>
        <IMGURL1></IMGURL1>
        <IMGURL2></IMGURL2>
        <IMGURL3></IMGURL3>
        <PRICE>3199.99</PRICE>
        <CURRENCY>EUR</CURRENCY>


        <YEAR>2015</YEAR>
        <AVAILABLE>NO</AVAILABLE>
    </SHOPITEM>
    <SHOPITEM>
        <CATEGORY>Full</CATEGORY>
        <WHEEL>27.5</WHEEL>
        <FRAMESIZE>MD</FRAMESIZE>
        <CODE>032,99</CODE>
        <PRODUCT>POINT</PRODUCT>
        <COLOR>red / green</COLOR>
        <NOTE>Available 15.2.2015</NOTE>
        <URL></URL>
        <IMGURL1></IMGURL1>
        <IMGURL2></IMGURL2>
        <IMGURL3></IMGURL3>
        <PRICE>3199.99</PRICE>
        <CURRENCY>EUR</CURRENCY>


        <YEAR>2015</YEAR>
        <AVAILABLE>NO</AVAILABLE>
    </SHOPITEM>
    <SHOPITEM>
        <CATEGORY>Full</CATEGORY>
        <WHEEL>27.5</WHEEL>
        <FRAMESIZE>LG</FRAMESIZE>
        <CODE>032,01</CODE>
        <PRODUCT>POINT</PRODUCT>
        <COLOR>black / white</COLOR>

        <NOTE>Available 15.2.2015</NOTE>
        <URL></URL>
        <IMGURL1></IMGURL1>
        <IMGURL2></IMGURL2>
        <IMGURL3></IMGURL3>
        <PRICE>3199.99</PRICE>
        <CURRENCY>EUR</CURRENCY>


        <YEAR>2015</YEAR>
        <AVAILABLE>NO</AVAILABLE>
    </SHOPITEM>
</SHOP>    

It is possible to distribute product options on same <PRODUCT>, like this:

<SHOPITEM>
    <CATEGORY>Full</CATEGORY>
    <WHEEL>27.5</WHEEL>
    <FRAMESIZE>LG</FRAMESIZE>
    <CODE>032,01</CODE>
    <PRODUCT>POINT</PRODUCT>
    <COLOR>black / white</COLOR>

<NOTE>Available 15.2.2015</NOTE>
<URL></URL>
<IMGURL1></IMGURL1>
<IMGURL2></IMGURL2>
<IMGURL3></IMGURL3>
<PRICE>3199.99</PRICE>
<CURRENCY>EUR</CURRENCY>
<YEAR>2015</YEAR>
<AVAILABLE>NO</AVAILABLE>

<PRODUCT_VARIANT id="2">
    <COLOR>red / green</COLOR>
    <FRAMESIZE>MD</FRAMESIZE>
    <CODE>032,99</CODE>
    <IMGURL1></IMGURL1>
    <IMGURL2></IMGURL2>
    <IMGURL3></IMGURL3>
    <AVAILABLE>NO</AVAILABLE>
    <NOTE>Available 15.2.2015</NOTE>
</PRODUCT_VARIANT>
<PRODUCT_VARIANT id="3">
    <COLOR>black / white</COLOR>
    <FRAMESIZE>LG</FRAMESIZE>
    <CODE>032,01</CODE>
    <IMGURL1></IMGURL1>
    <IMGURL2></IMGURL2>
    <IMGURL3></IMGURL3>
    <AVAILABLE>NO</AVAILABLE>
        <NOTE>Available 15.2.2015</NOTE>
    </PRODUCT_VARIANT>
</SHOPITEM>