RepositoryBrowser is updated to support auto registration.

Refactored the ConcurrentHashMap double-if putIfAbsent idiom into the Memoizer class.

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@15653 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/ExtensionPoint.java

@@ -23,6 +23,13 @@
  */
 package hudson;
 
+import hudson.model.Hudson;
+
+import static java.lang.annotation.ElementType.TYPE;
+import java.lang.annotation.Retention;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+import java.lang.annotation.Target;
+
 /**
  * Marker interface that designates extensible components
  * in Hudson that can be implemented by plugins.
@@ -41,4 +48,12 @@ package hudson;
  * @see Extension
  */
 public interface ExtensionPoint {
+    /**
+     * Used by designers of extension points (direct subtypes of {@link ExtensionPoint}) to indicate that
+     * the legacy instances are scoped to {@link Hudson} instance. By default, legacy instances are
+     * static scope.  
+     */
+    @Target(TYPE)
+    @Retention(RUNTIME)
+    public @interface LegacyInstancesAreScopedToHudson {}
 }