Fixed issue 4, with fine control over the tabs access.

For each tab, at the exception of the project home and the
administration area, it possible to control the access rights if the
user is anonymous, signed in, member or owner.

src/IDF/Precondition.php

@@ -61,4 +61,53 @@ class IDF_Precondition
         }
         return new Pluf_HTTP_Response_Forbidden($request);
     }
+
+    /**
+     * Check if the user can access a given element.
+     *
+     * The rights are:
+     *  - 'all' (default)
+     *  - 'none'
+     *  - 'login'
+     *  - 'members'
+     *  - 'owners'
+     *
+     * The order of the rights is such that a 'owner' is also a
+     * 'member' and of course a logged in person.
+     *
+     * @param Pluf_HTTP_Request
+     * @param string Control key
+     * @return mixed
+     */
+    static public function accessTabGeneric($request, $key)
+    {
+        switch ($request->conf->getVal($key, 'all')) {
+        case 'none':
+            return new Pluf_HTTP_Response_Forbidden($request);
+        case 'login':
+            return Pluf_Precondition::loginRequired($request);
+        case 'members':
+            return self::projectMemberOrOwner($request);
+        case 'owners':
+            return self::projectOwner($request);
+        case 'all':
+        default:
+            return true;
+        }
+    }
+
+    static public function accessSource($request)
+    {
+        return self::accessTabGeneric($request, 'source_access_rights');
+    }
+
+    static public function accessIssues($request)
+    {
+        return self::accessTabGeneric($request, 'issues_access_rights');
+    }
+
+    static public function accessDownloads($request)
+    {
+        return self::accessTabGeneric($request, 'downloads_access_rights');
+    }
 }