added an indirection so that clever Descriptor can alter the new

core/src/main/resources/hudson/model/Descriptor/newInstanceDetail.jelly

+<!--
+The MIT License
+
+Copyright (c) 2010, CloudBees, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+-->
+
+<j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define" xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form" xmlns:i="jelly:fmt">
+  <!--
+    Used to render the description under a radio button in the "new job/computer/etc" page.
+    By default we further delegate it to clazz, but this hook allows Descriptors to
+    do something more sophisticated if needed.
+  -->
+  <st:include page="newInstanceDetail.jelly" class="${it.clazz}" optional="true"/>
+</j:jelly>

core/src/main/resources/hudson/model/Job/newInstanceDetail.jelly

+<!--
+The MIT License
+
+Copyright (c) 2010, CloudBees, Inc.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+-->
+
+<j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define" xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form" xmlns:i="jelly:fmt">
+  <!--
+    For historical reasons, jobs used "newJobDetail.jelly".
+
+    "it" is a descriptor when this file is called.
+  -->
+  <st:include page="newJobDetail.jelly" class="${it.clazz}" optional="true"/>
+</j:jelly>

core/src/main/resources/lib/hudson/newFromList/form.jelly

 <!--
 The MIT License
 
-Copyright (c) 2004-2009, Sun Microsystems, Inc., Kohsuke Kawaguchi, Yahoo! Inc.
+Copyright (c) 2004-2009, Sun Microsystems, Inc., Kohsuke Kawaguchi, Yahoo! Inc., CloudBees, Inc.
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
@@ -48,7 +48,7 @@ THE SOFTWARE.
       </s:block>
       <s:entry>
         <st:set var="instance" value="${descriptor}" />
-        <st:include page="newJobDetail.jelly" class="${descriptor.clazz}" optional="true"/>
+        <st:include page="newInstanceDetail.jelly" it="${descriptor}" />
       </s:entry>
     </j:forEach>
     <j:if test="${!empty(copyNames)}">