--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/org/tmatesoft/hg/internal/Callback.java	Fri Mar 23 22:51:18 2012 +0100
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2012 TMate Software Ltd
+ *  
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * For information on how to redistribute this software under
+ * the terms of a license other than GNU General Public License
+ * contact TMate Software at support@hg4j.com
+ */
+package org.tmatesoft.hg.internal;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import org.tmatesoft.hg.core.HgCallbackTargetException;
+
+/**
+ * Marker to ease location of callback interfaces in the API.
+ * 
+ * All classes/interfaces supposed to be subclassed/implemented by users, with methods throwing {@link HgCallbackTargetException} shall bear the mark.
+ * Besides, classes that are low-level callbacks (from {@link org.tmatesoft.hg.repo}) shall bear it, too.
+ * 
+ * @author Artem Tikhomirov
+ * @author TMate Software Ltd.
+ */
+@Retention(RetentionPolicy.SOURCE)
+@Target({ ElementType.TYPE })
+public @interface Callback {
+}