force the backend to inherit item class

- Now each backend have to define an item class like repository case
because the name of the class is declared on the backend class, and now base
item class is abstract.

includes/VersioncontrolItem.php

@@ -35,7 +35,7 @@
  * applicable. Most item revisions, but probably not all of them, are recorded
  * in the database.
  */
-class VersioncontrolItem implements ArrayAccess {
+abstract class VersioncontrolItem implements ArrayAccess {
     // Attributes
     /**
      * db identifier
@@ -544,7 +544,7 @@ public function getParentItem($parent_path = NULL) {
         $revision = $this->revision;
       }
 
-      $parent_item = new VersioncontrolItem(VERSIONCONTROL_ITEM_DIRECTORY,
+      $parent_item = new $this->repository->backend->classes['item'](VERSIONCONTROL_ITEM_DIRECTORY,
         $path, $revision, NULL, $this->repository);
 
       $parent_item->selected_label = new stdClass();

includes/VersioncontrolOperation.php

@@ -480,7 +480,7 @@ public function getItems($fetch_source_items = NULL) {
         $this->vc_op_id, VERSIONCONTROL_OPERATION_MEMBER_ITEM);
 
       while ($item_revision = db_fetch_object($result)) {
-        $items[$item_revision->path] = new VersioncontrolItem($item_revision->type, $item_revision->path, $item_revision->revision, NULL, $this->repository, NULL, $item_revision->item_revision_id);
+        $items[$item_revision->path] = new $this->repository->backend->classes['item']($item_revision->type, $item_revision->path, $item_revision->revision, NULL, $this->repository, NULL, $item_revision->item_revision_id);
         $items[$item_revision->path]->selected_label = new stdClass();
         $items[$item_revision->path]->selected_label->get_from = 'operation';
         $items[$item_revision->path]->selected_label->operation = &$this;

tests/versioncontrol_test.module

@@ -32,6 +32,7 @@ class VersioncontrolTestBackend extends VersioncontrolBackend {
       'repo' => 'VersioncontrolTestRepository',
       'account' => 'VersioncontrolTestAccount',
       'operation' => 'VersioncontrolTestOperation',
+      'item' => 'VersioncontrolTestItem',
     );
   }
 }
@@ -44,3 +45,6 @@ class VersioncontrolTestAccount extends VersioncontrolAccount {
 
 class VersioncontrolTestOperation extends VersioncontrolOperation {
 }
+
+class VersioncontrolTestItem extends VersioncontrolItem {
+}

versioncontrol.module

@@ -1059,7 +1059,7 @@ function versioncontrol_fetch_source_items($repository, &$items) {
       $items[$successor_key]->source_items = array();
     }
 
-    $item = new VersioncontrolItem(
+    $item = new $repository->backend->classes['item'](
       $item_revision->type,
       $item_revision->path,
       $item_revision->revision,