Admin: add a duplicate field command

* wcs/admin/fields.ptl:
   add a duplicate field command, that:
    - use 'copy' module to copy the Field object
    - find a new id, and
    - insert just after the copied field.

wcs/admin/fields.ptl

@@ -13,6 +13,7 @@ from qommon.admin.menu import html_top, command_icon, error_page
 from wcs import fields
 from wcs.formdef import FormDef
 from wcs.fields import get_field_types
+import copy
 
 class FieldWidget(CompositeWidget):
     large = False
@@ -50,7 +51,7 @@ class FieldWidget(CompositeWidget):
 
 
 class FieldDefPage(Directory):
-    _q_exports = ['', 'delete', 'down', 'up', 'ajaxtitle']
+    _q_exports = ['', 'delete', 'down', 'up', 'ajaxtitle', 'duplicate']
 
     large = False
     section = None
@@ -133,6 +134,22 @@ class FieldDefPage(Directory):
             self.objectdef.store()
             return redirect('../../fields/')
 
+    def duplicate(self):
+        field_pos = self.objectdef.fields.index(self.field)
+        fields = self.objectdef.fields
+        new_field = copy.copy(self.field)
+        def lax_int(s):
+            try:
+                return int(s)
+            except (ValueError, TypeError):
+                return -1
+        # allocate a new id
+        id = str(max([lax_int(x.id) for x in self.objectdef.fields]) + 1)
+        new_field.id = id
+        fields.insert(field_pos+1, new_field)
+        self.objectdef.store()
+        return redirect('../../fields/')
+
     def down(self):
         field_pos = self.objectdef.fields.index(self.field)
         fields = self.objectdef.fields
@@ -242,7 +259,7 @@ class FieldsDirectory(Directory):
                         command_icon('?page=%s' % current_page_no, 'view',
                                 label = _('Limit display to this page'))
                     command_icon('%s/' % field.id, 'edit')
-
+                command_icon('%s/duplicate' % field.id, 'duplicate')
                 command_icon('%s/delete' % field.id, 'remove', popup = True)
                 '</p></li>'
             '</ul>'