added @Default

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@33061 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/resources/lib/form/textarea.jelly

@@ -40,6 +40,9 @@ THE SOFTWARE.
       will be set as the initial value automatically,
       which is the recommended approach.
     </st:attribute>
+    <st:attribute name="default">
+      The default value of the text box, in case both @value is and 'instance[field]' is null.
+    </st:attribute>
     <st:attribute name="checkUrl">
       If specified, the value entered in this input field will be checked (via AJAX)
       against this URL, and errors will be rendered under the text field.
@@ -55,7 +58,7 @@ THE SOFTWARE.
             class="setting-input ${attrs.checkUrl!=null?'validated':''} ${attrs.class}"
             checkUrl="${attrs.checkUrl}"
             rows="${h.determineRows(attrs.value)}">
-    <st:out value="${attrs.value ?: instance[attrs.field]}" />
+    <st:out value="${attrs.value ?: instance[attrs.field] ?: attrs.default}" />
   </textarea>
   <!-- resize handle -->
   <div class="textarea-handle"/>