Update copy.xsl

* Fix: update schema reference URI to match actual local path
* Fix: add missing attributes on TEI element
* Fix: remove empty `@xml:lang` on xicluded elements
* Fix: remove surplus xml-lang prcessing-instructions from xincluded files
* Fix: remove `@xml:base` on xincluded files as those would render all relative targets unavailable

utils/canonicalization/copy.xsl

@@ -3,9 +3,10 @@
     xmlns:xs="http://www.w3.org/2001/XMLSchema"
     xmlns:math="http://www.w3.org/2005/xpath-functions/math"
     xmlns:xd="http://www.oxygenxml.com/ns/doc/xsl"
+    xmlns:xi="http://www.w3.org/2001/XInclude"
     xmlns:tei="http://www.tei-c.org/ns/1.0"
     xmlns="http://www.tei-c.org/ns/1.0"
-    exclude-result-prefixes="xs math xd"
+    exclude-result-prefixes="xsl xs math xd xi" 
     version="3.0">
     <xd:doc scope="stylesheet">
         <xd:desc>
@@ -17,33 +18,55 @@
 
     <xsl:output indent="false"></xsl:output>
 
-    <xsl:template match="node()|@*">
+    <xsl:template match="node()|@*" mode="#all">
         <xsl:copy>
-            <xsl:apply-templates select="@*|node()"/>
+            <xsl:apply-templates select="@*|node()" mode="#current"/>
         </xsl:copy>
     </xsl:template>
 
-    <xsl:template match="processing-instruction('xml-model')">
-        <xsl:text>&#xa;</xsl:text>
+    <xsl:template match="processing-instruction('xml-model')" mode="clone">
         <xsl:copy/>
     </xsl:template>
 
+    <xsl:template match="processing-instruction('xml-model')" mode="cleanup"/>
+
+    <xsl:template match="/processing-instruction('xml-model')" mode="cleanup">
+        <xsl:variable name="pi-value.tokens" select="tokenize(., ' ')"/>
+        <xsl:variable name="pi-href" select="replace($pi-value.tokens[1], '&quot;validation/', '../../../source/&quot;validation/' )"/>
+        <xsl:text>&#xa;</xsl:text>
+        <xsl:processing-instruction name="xml-model">
+            <xsl:value-of select="$pi-href, $pi-value.tokens[position() > 1]" separator=" "/>
+        </xsl:processing-instruction>
+    </xsl:template>
+
     <xsl:template match="/">
+        <xsl:variable name="xincluded">
+            <xsl:apply-templates/>
+        </xsl:variable>
+        <xsl:apply-templates select="$xincluded" mode="cleanup"/>
+    </xsl:template>
+
+    <xsl:template match="/" mode="cleanup">
         <xsl:text>&#xa;</xsl:text>
         <xsl:copy>
-            <xsl:apply-templates select="node()"/>
+            <xsl:apply-templates select="node()" mode="cleanup"/>
         </xsl:copy>
     </xsl:template>
 
-    <xsl:template match="tei:TEI">
+    <xsl:template match="tei:TEI" mode="cleanup">
         <xsl:text>&#xa;</xsl:text>
         <xsl:comment>
             <xsl:text>canonicalized: </xsl:text>
             <xsl:value-of select="current-dateTime()"/>
         </xsl:comment>
         <xsl:text>&#xa;</xsl:text>
         <xsl:copy>
-            <xsl:apply-templates select="node()"/>
+            <xsl:apply-templates select="@*"/>
+            <xsl:apply-templates select="node()" mode="cleanup"/>
         </xsl:copy>
     </xsl:template>
-</xsl:stylesheet>
+
+    <xsl:template match="@xml:lang[. = '']" mode="cleanup"/>
+
+    <xsl:template match="@xml:base" mode="cleanup"/>
+</xsl:stylesheet>