Configure WindowCache settings to use in JGit CLI

Set the same defaults as in EGit.
Use mmap to map git packfiles into memory.

Change-Id: I7997b9123448a762192d7eeb55e01432549fba98
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Main.java

 import org.eclipse.jgit.pgm.internal.CLIText;
 import org.eclipse.jgit.pgm.opt.CmdLineParser;
 import org.eclipse.jgit.pgm.opt.SubcommandHandler;
+import org.eclipse.jgit.storage.file.WindowCacheConfig;
 import org.eclipse.jgit.transport.HttpTransport;
 import org.eclipse.jgit.transport.http.apache.HttpClientConnectionFactory;
 import org.eclipse.jgit.util.CachedAuthenticator;
 
 	private ExecutorService gcExecutor;
 
+	private static final int MB = 1024 * 1024;
+
 	/**
 	 * <p>Constructor for Main.</p>
 	 */
 	public Main() {
+		final WindowCacheConfig c = new WindowCacheConfig();
+		c.setPackedGitMMAP(true);
+		c.setPackedGitWindowSize(8 * 1024);
+		c.setPackedGitLimit(10 * MB);
+		c.setDeltaBaseCacheLimit(10 * MB);
+		c.setStreamFileThreshold(50 * MB);
+		c.install();
 		HttpTransport.setConnectionFactory(new HttpClientConnectionFactory());
 		BuiltinLFS.register();
 		gcExecutor = Executors.newSingleThreadExecutor(new ThreadFactory() {