Update HasMany show collection partial path (#2)

Built on thoughtbot#522

app/views/fields/has_many/_show.html.erb

@@ -22,7 +22,7 @@ from the associated resource class's dashboard.
   <% order = field.order_from_params(params.fetch(field.name, {})) %>
   <% page_number = params.fetch(field.name, {}).fetch(:page, nil) %>
   <%= render(
-    "collection",
+    field.collection_partial(namespace),
     collection_presenter: field.associated_collection(order),
     collection_field_name: field.name,
     page: page,

lib/administrate/field/has_many.rb

@@ -35,6 +35,21 @@ def associated_resource_options
         end
       end
 
+      def collection_partial(namespace)
+        partial = 'collection'
+        prefix = options[:class_name].try(:underscore).try(:pluralize) || name
+        view_paths = ActionView::PathSet.new(["app/views/#{namespace}"])
+        lookup_context = ActionView::LookupContext.new(view_paths)
+
+        resouce_template_exists = lookup_context.exists?(partial, [namespace, prefix], true)
+        return [namespace, prefix, partial].join('/') if resouce_template_exists
+
+        application_template_exists = lookup_context.exists?(partial, [namespace, '/'], true)
+        return [namespace, partial].join('/') if application_template_exists
+
+        ['administrate', 'application', partial].join('/')
+      end
+
       def selected_options
         return if data.empty?