Add the an event and listener for a dfs PackIndex being loaded.

The DfsPackFile will fire any static repository listeners on the event
just before the PackIndex is loaded.

Change-Id: Ie51098106bd5a1a32feae7d2dd068abf02b030ee

org.eclipse.jgit/src/org/eclipse/jgit/storage/dfs/BeforeDfsPackIndexLoadedEvent.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2012, Google Inc.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.storage.dfs;
+
+import org.eclipse.jgit.events.RepositoryEvent;
+
+/**
+ * Describes the {@link DfsPackFile} just before its index is loaded. Currently,
+ * DfsPackFile directly dispatches the event on
+ * {@link org.eclipse.jgit.lib.Repository#getGlobalListenerList}. Which means
+ * the call to {@link #getRepository} will always return null.
+ */
+public class BeforeDfsPackIndexLoadedEvent
+		extends RepositoryEvent<BeforeDfsPackIndexLoadedListener> {
+	private final DfsPackFile pack;
+
+	/**
+	 * A new event triggered before a PackFile index is loaded.
+	 *
+	 * @param pack
+	 *            the pack
+	 */
+	public BeforeDfsPackIndexLoadedEvent(DfsPackFile pack) {
+		this.pack = pack;
+	}
+
+	/** @return the PackFile containing the index that will be loaded. */
+	public DfsPackFile getPackFile() {
+		return pack;
+	}
+
+	@Override
+	public Class<BeforeDfsPackIndexLoadedListener> getListenerType() {
+		return BeforeDfsPackIndexLoadedListener.class;
+	}
+
+	@Override
+	public void dispatch(BeforeDfsPackIndexLoadedListener listener) {
+		listener.onBeforeDfsPackIndexLoaded(this);
+	}
+}

org.eclipse.jgit/src/org/eclipse/jgit/storage/dfs/BeforeDfsPackIndexLoadedListener.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2012, Google Inc.
+ * and other copyright owners as documented in the project's IP log.
+ *
+ * This program and the accompanying materials are made available
+ * under the terms of the Eclipse Distribution License v1.0 which
+ * accompanies this distribution, is reproduced below, and is
+ * available at http://www.eclipse.org/org/documents/edl-v10.php
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package org.eclipse.jgit.storage.dfs;
+
+import org.eclipse.jgit.events.RepositoryListener;
+
+/** Receives {@link BeforeDfsPackIndexLoadedEvent}s. */
+public interface BeforeDfsPackIndexLoadedListener extends RepositoryListener {
+	/**
+	 * Invoked just before a pack index is loaded from the block cache.
+	 *
+	 * @param event
+	 *            information about the packs.
+	 */
+	void onBeforeDfsPackIndexLoaded(BeforeDfsPackIndexLoadedEvent event);
+}

org.eclipse.jgit/src/org/eclipse/jgit/storage/dfs/DfsPackFile.java

@@ -67,6 +67,7 @@ import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectLoader;
+import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.storage.file.PackIndex;
 import org.eclipse.jgit.storage.file.PackReverseIndex;
 import org.eclipse.jgit.storage.pack.BinaryDelta;
@@ -212,6 +213,9 @@ public final class DfsPackFile {
 		if (invalid)
 			throw new PackInvalidException(getPackName());
 
+		Repository.getGlobalListenerList()
+				.dispatch(new BeforeDfsPackIndexLoadedEvent(this));
+
 		synchronized (initLock) {
 			idxref = index;
 			if (idxref != null) {