Editor / Fix attribute editing when using a template mode field.

If the attribute was present in both the template snippet and
the matching node, then the template was only containing the one
from the node (and the attribute value was not editable).

web/src/main/webapp/xslt/common/utility-tpl-metadata.xsl

@@ -75,10 +75,22 @@
 
     <xsl:variable name="nodeName" select="name(.)"/>
     <xsl:variable name="parentName" select="name(..)"/>
+    <xsl:variable name="attrs" select="@*"/>
 
     <xsl:copy>
-      <xsl:copy-of
-        select="@*|$node-to-merge/descendant-or-self::node()[name() = $nodeName and name(..) = $parentName]/@*"/>
+      <!-- Copy all attribute from the template mode first
+       and then all existing attributes of the equivalent node
+       which are not defined in the template (to avoid to override
+       the template attribute by the matching node ones). -->
+      <xsl:copy-of select="$attrs"/>
+      <xsl:for-each select="$node-to-merge/descendant-or-self::node()[
+                              name() = $nodeName and name(..) = $parentName
+                            ]/@*">
+        <xsl:variable name="attrName" select="name()"/>
+        <xsl:if test="count($attrs[name() = $attrName]) = 0">
+          <xsl:copy-of select="."/>
+        </xsl:if>
+      </xsl:for-each>
       <xsl:apply-templates mode="gn-merge" select="*">
         <xsl:with-param name="node-to-merge" select="$node-to-merge"/>
       </xsl:apply-templates>