Make StoredConfig an abstraction above FileBasedConfig

This exposes a load and save method, allowing a Repository to denote
that it has a persistent configuration of some kind which can be
accessed by the application, without needing to know exact details
of how its stored .

Change-Id: I7c414bc0f975b80f083084ea875eca25c75a07b2
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

org.eclipse.jgit/src/org/eclipse/jgit/lib/Repository.java

@@ -199,7 +199,7 @@ public abstract class Repository {
 	/**
 	 * @return the configuration of this repository
 	 */
-	public abstract Config getConfig();
+	public abstract StoredConfig getConfig();
 
 	/**
 	 * @return the used file system abstraction

org.eclipse.jgit/src/org/eclipse/jgit/lib/StoredConfig.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2010, 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.lib;
+
+import java.io.IOException;
+
+import org.eclipse.jgit.errors.ConfigInvalidException;
+
+/**
+ * Persistent configuration that can be stored and loaded from a location.
+ */
+public abstract class StoredConfig extends Config {
+	/** Create a configuration with no default fallback. */
+	public StoredConfig() {
+		super();
+	}
+
+	/**
+	 * Create an empty configuration with a fallback for missing keys.
+	 *
+	 * @param defaultConfig
+	 *            the base configuration to be consulted when a key is missing
+	 *            from this configuration instance.
+	 */
+	public StoredConfig(Config defaultConfig) {
+		super(defaultConfig);
+	}
+
+	/**
+	 * Load the configuration from the persistent store.
+	 * <p>
+	 * If the configuration does not exist, this configuration is cleared, and
+	 * thus behaves the same as though the backing store exists, but is empty.
+	 *
+	 * @throws IOException
+	 *             the configuration could not be read (but does exist).
+	 * @throws ConfigInvalidException
+	 *             the configuration is not properly formatted.
+	 */
+	public abstract void load() throws IOException, ConfigInvalidException;
+
+	/**
+	 * Save the configuration to the persistent store.
+	 *
+	 * @throws IOException
+	 *             the configuration could not be written.
+	 */
+	public abstract void save() throws IOException;
+}

org.eclipse.jgit/src/org/eclipse/jgit/storage/file/FileBasedConfig.java

@@ -58,13 +58,14 @@ import org.eclipse.jgit.JGitText;
 import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.StoredConfig;
 import org.eclipse.jgit.util.IO;
 import org.eclipse.jgit.util.RawParseUtils;
 
 /**
  * The configuration file that is stored in the file of the file system.
  */
-public class FileBasedConfig extends Config {
+public class FileBasedConfig extends StoredConfig {
 	private final File configFile;
 	private volatile long lastModified;
 
@@ -107,6 +108,7 @@ public class FileBasedConfig extends Config {
 	 * @throws ConfigInvalidException
 	 *             the file is not a properly formatted configuration file.
 	 */
+	@Override
 	public void load() throws IOException, ConfigInvalidException {
 		lastModified = getFile().lastModified();
 		try {