/*
    * Copyright (C) 2008-2010, 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.transport;
  
  import static org.eclipse.jgit.lib.RefDatabase.ALL;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_AGENT;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_ALLOW_TIP_SHA1_IN_WANT;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_INCLUDE_TAG;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_MULTI_ACK;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_MULTI_ACK_DETAILED;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_NO_DONE;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_NO_PROGRESS;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_OFS_DELTA;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_SHALLOW;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_SIDE_BAND;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_SIDE_BAND_64K;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_THIN_PACK;
  
  import java.io.EOFException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.text.MessageFormat;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  
  import org.eclipse.jgit.errors.CorruptObjectException;
  import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.errors.PackProtocolException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.internal.storage.pack.PackWriter;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.NullProgressMonitor;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ProgressMonitor;
  import org.eclipse.jgit.lib.Ref;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.revwalk.AsyncRevObjectQueue;
  import org.eclipse.jgit.revwalk.DepthWalk;
  import org.eclipse.jgit.revwalk.ObjectWalk;
  import org.eclipse.jgit.revwalk.RevCommit;
  import org.eclipse.jgit.revwalk.RevFlag;
  import org.eclipse.jgit.revwalk.RevFlagSet;
  import org.eclipse.jgit.revwalk.RevObject;
  import org.eclipse.jgit.revwalk.RevTag;
  import org.eclipse.jgit.revwalk.RevWalk;
  import org.eclipse.jgit.revwalk.filter.CommitTimeRevFilter;
  import org.eclipse.jgit.storage.pack.PackConfig;
  import org.eclipse.jgit.transport.GitProtocolConstants.MultiAck;
  import org.eclipse.jgit.transport.RefAdvertiser.PacketLineOutRefAdvertiser;
  import org.eclipse.jgit.util.io.InterruptTimer;
  import org.eclipse.jgit.util.io.NullOutputStream;
 import org.eclipse.jgit.util.io.TimeoutInputStream;
 import org.eclipse.jgit.util.io.TimeoutOutputStream;
 
 /**
  * Implements the server side of a fetch connection, transmitting objects.
  */
 public class UploadPack {
 	/** Policy the server uses to validate client requests */
 	public static enum RequestPolicy {
 		/** Client may only ask for objects the server advertised a reference for. */
 		ADVERTISED,
 
 		/**
 		 * Client may ask for any commit reachable from a reference advertised by
 		 * the server.
 		 */
 		REACHABLE_COMMIT,
 
 		/**
 		 * Client may ask for objects that are the tip of any reference, even if not
 		 * advertised.
 		 * <p>
 		 * This may happen, for example, when a custom {@link RefFilter} is set.
 		 *
 		 * @since 3.1
 		 */
 		TIP,
 
 		/**
 		 * Client may ask for any commit reachable from any reference, even if that
 		 * reference wasn't advertised.
 		 *
 		 * @since 3.1
 		 */
 		REACHABLE_COMMIT_TIP,
 
 		/** Client may ask for any SHA-1 in the repository. */
 		ANY;
 	}
 
 	/**
 	 * Validator for client requests.
 	 *
 	 * @since 3.1
 	 */
 	public interface RequestValidator {
 		/**
 		 * Check a list of client wants against the request policy.
 		 *
 		 * @param up
 		 *            {@link UploadPack} instance.
 		 * @param wants
 		 *            objects the client requested that were not advertised.
 		 *
 		 * @throws PackProtocolException
 		 *            if one or more wants is not valid.
 		 * @throws IOException
 		 *            if a low-level exception occurred.
 		 * @since 3.1
 		 */
 		void checkWants(UploadPack up, List<ObjectId> wants)
 				throws PackProtocolException, IOException;
 	}
 
 	/** Data in the first line of a request, the line itself plus options. */
 	public static class FirstLine {
 		private final String line;
 		private final Set<String> options;
 
 		/**
 		 * Parse the first line of a receive-pack request.
 		 *
 		 * @param line
 		 *            line from the client.
 		 */
 		public FirstLine(String line) {
 			if (line.length() > 45) {
 				final HashSet<String> opts = new HashSet<String>();
 				String opt = line.substring(45);
 				if (opt.startsWith(" ")) //$NON-NLS-1$
 					opt = opt.substring(1);
 				for (String c : opt.split(" ")) //$NON-NLS-1$
 					opts.add(c);
 				this.line = line.substring(0, 45);
 				this.options = Collections.unmodifiableSet(opts);
 			} else {
 				this.line = line;
 				this.options = Collections.emptySet();
 			}
 		}
 
 		/** @return non-capabilities part of the line. */
 		public String getLine() {
 			return line;
 		}
 
 		/** @return options parsed from the line. */
 		public Set<String> getOptions() {
 			return options;
 		}
 	}
 
 	/** Database we read the objects from. */
 	private final Repository db;
 
 	/** Revision traversal support over {@link #db}. */
 	private final RevWalk walk;
 
 	/** Configuration to pass into the PackWriter. */
 	private PackConfig packConfig;
 
 	/** Configuration for various transfer options. */
 	private TransferConfig transferConfig;
 
 	/** Timeout in seconds to wait for client interaction. */
 	private int timeout;
 
 	/**
 	 * Is the client connection a bi-directional socket or pipe?
 	 * <p>
 	 * If true, this class assumes it can perform multiple read and write cycles
 	 * with the client over the input and output streams. This matches the
 	 * functionality available with a standard TCP/IP connection, or a local
 	 * operating system or in-memory pipe.
 	 * <p>
 	 * If false, this class runs in a read everything then output results mode,
 	 * making it suitable for single round-trip systems RPCs such as HTTP.
 	 */
 	private boolean biDirectionalPipe = true;
 
 	/** Timer to manage {@link #timeout}. */
 	private InterruptTimer timer;
 
 	private InputStream rawIn;
 
 	private OutputStream rawOut;
 
 	private PacketLineIn pckIn;
 
 	private PacketLineOut pckOut;
 
 	private OutputStream msgOut = NullOutputStream.INSTANCE;
 
 	/** The refs we advertised as existing at the start of the connection. */
 	private Map<String, Ref> refs;
 
 	/** Hook used while advertising the refs to the client. */
 	private AdvertiseRefsHook advertiseRefsHook = AdvertiseRefsHook.DEFAULT;
 
 	/** Filter used while advertising the refs to the client. */
 	private RefFilter refFilter = RefFilter.DEFAULT;
 
 	/** Hook handling the various upload phases. */
 	private PreUploadHook preUploadHook = PreUploadHook.NULL;
 
 	/** Capabilities requested by the client. */
 	private Set<String> options;
 	String userAgent;
 
 	/** Raw ObjectIds the client has asked for, before validating them. */
 	private final Set<ObjectId> wantIds = new HashSet<ObjectId>();
 
 	/** Objects the client wants to obtain. */
 	private final Set<RevObject> wantAll = new HashSet<RevObject>();
 
 	/** Objects on both sides, these don't have to be sent. */
 	private final Set<RevObject> commonBase = new HashSet<RevObject>();
 
 	/** Shallow commits the client already has. */
 	private final Set<ObjectId> clientShallowCommits = new HashSet<ObjectId>();
 
 	/** Shallow commits on the client which are now becoming unshallow */
 	private final List<ObjectId> unshallowCommits = new ArrayList<ObjectId>();
 
 	/** Desired depth from the client on a shallow request. */
 	private int depth;
 
 	/** Commit time of the oldest common commit, in seconds. */
 	private int oldestTime;
 
 	/** null if {@link #commonBase} should be examined again. */
 	private Boolean okToGiveUp;
 
 	private boolean sentReady;
 
 	/** Objects we sent in our advertisement list, clients can ask for these. */
 	private Set<ObjectId> advertised;
 
 	/** Marked on objects the client has asked us to give them. */
 	private final RevFlag WANT;
 
 	/** Marked on objects both we and the client have. */
 	private final RevFlag PEER_HAS;
 
 	/** Marked on objects in {@link #commonBase}. */
 	private final RevFlag COMMON;
 
 	/** Objects where we found a path from the want list to a common base. */
 	private final RevFlag SATISFIED;
 
 	private final RevFlagSet SAVE;
 
 	private RequestValidator requestValidator = new AdvertisedRequestValidator();
 
 	private MultiAck multiAck = MultiAck.OFF;
 
 	private boolean noDone;
 
 	private PackWriter.Statistics statistics;
 
 	private UploadPackLogger logger = UploadPackLogger.NULL;
 
 	/**
 	 * Create a new pack upload for an open repository.
 	 *
 	 * @param copyFrom
 	 *            the source repository.
 	 */
 	public UploadPack(final Repository copyFrom) {
 		db = copyFrom;
 		walk = new RevWalk(db);
 		walk.setRetainBody(false);
 
 		WANT = walk.newFlag("WANT"); //$NON-NLS-1$
 		PEER_HAS = walk.newFlag("PEER_HAS"); //$NON-NLS-1$
 		COMMON = walk.newFlag("COMMON"); //$NON-NLS-1$
 		SATISFIED = walk.newFlag("SATISFIED"); //$NON-NLS-1$
 		walk.carry(PEER_HAS);
 
 		SAVE = new RevFlagSet();
 		SAVE.add(WANT);
 		SAVE.add(PEER_HAS);
 		SAVE.add(COMMON);
 		SAVE.add(SATISFIED);
 
 		setTransferConfig(null);
 	}
 
 	/** @return the repository this upload is reading from. */
 	public final Repository getRepository() {
 		return db;
 	}
 
 	/** @return the RevWalk instance used by this connection. */
 	public final RevWalk getRevWalk() {
 		return walk;
 	}
 
 	/**
 	 * Get refs which were advertised to the client.
 	 *
 	 * @return all refs which were advertised to the client, or null if
 	 *         {@link #setAdvertisedRefs(Map)} has not been called yet.
 	 */
 	public final Map<String, Ref> getAdvertisedRefs() {
 		return refs;
 	}
 
 	/**
 	 * Set the refs advertised by this UploadPack.
 	 * <p>
 	 * Intended to be called from a {@link PreUploadHook}.
 	 *
 	 * @param allRefs
 	 *            explicit set of references to claim as advertised by this
 	 *            UploadPack instance. This overrides any references that
 	 *            may exist in the source repository. The map is passed
 	 *            to the configured {@link #getRefFilter()}. If null, assumes
 	 *            all refs were advertised.
 	 */
 	public void setAdvertisedRefs(Map<String, Ref> allRefs) {
 		if (allRefs != null)
 			refs = allRefs;
 		else
 			refs = db.getAllRefs();
 		if (refFilter == RefFilter.DEFAULT)
 			refs = transferConfig.getRefFilter().filter(refs);
 		else
 			refs = refFilter.filter(refs);
 	}
 
 	/** @return timeout (in seconds) before aborting an IO operation. */
 	public int getTimeout() {
 		return timeout;
 	}
 
 	/**
 	 * Set the timeout before willing to abort an IO call.
 	 *
 	 * @param seconds
 	 *            number of seconds to wait (with no data transfer occurring)
 	 *            before aborting an IO read or write operation with the
 	 *            connected client.
 	 */
 	public void setTimeout(final int seconds) {
 		timeout = seconds;
 	}
 
 	/**
 	 * @return true if this class expects a bi-directional pipe opened between
 	 *         the client and itself. The default is true.
 	 */
 	public boolean isBiDirectionalPipe() {
 		return biDirectionalPipe;
 	}
 
 	/**
 	 * @param twoWay
 	 *            if true, this class will assume the socket is a fully
 	 *            bidirectional pipe between the two peers and takes advantage
 	 *            of that by first transmitting the known refs, then waiting to
 	 *            read commands. If false, this class assumes it must read the
 	 *            commands before writing output and does not perform the
 	 *            initial advertising.
 	 */
 	public void setBiDirectionalPipe(final boolean twoWay) {
 		biDirectionalPipe = twoWay;
 	}
 
 	/**
 	 * @return policy used by the service to validate client requests, or null for
 	 *         a custom request validator.
 	 */
 	public RequestPolicy getRequestPolicy() {
 		if (requestValidator instanceof AdvertisedRequestValidator)
 			return RequestPolicy.ADVERTISED;
 		if (requestValidator instanceof ReachableCommitRequestValidator)
 			return RequestPolicy.REACHABLE_COMMIT;
 		if (requestValidator instanceof TipRequestValidator)
 			return RequestPolicy.TIP;
 		if (requestValidator instanceof ReachableCommitTipRequestValidator)
 			return RequestPolicy.REACHABLE_COMMIT_TIP;
 		if (requestValidator instanceof AnyRequestValidator)
 			return RequestPolicy.ANY;
 		return null;
 	}
 
 	/**
 	 * @param policy
 	 *            the policy used to enforce validation of a client's want list.
 	 *            By default the policy is {@link RequestPolicy#ADVERTISED},
 	 *            which is the Git default requiring clients to only ask for an
 	 *            object that a reference directly points to. This may be relaxed
 	 *            to {@link RequestPolicy#REACHABLE_COMMIT} or
 	 *            {@link RequestPolicy#REACHABLE_COMMIT_TIP} when callers have
 	 *            {@link #setBiDirectionalPipe(boolean)} set to false.
 	 *            Overrides any policy specified in a {@link TransferConfig}.
 	 */
 	public void setRequestPolicy(RequestPolicy policy) {
 		switch (policy) {
 			case ADVERTISED:
 			default:
 				requestValidator = new AdvertisedRequestValidator();
 				break;
 			case REACHABLE_COMMIT:
 				requestValidator = new ReachableCommitRequestValidator();
 				break;
 			case TIP:
 				requestValidator = new TipRequestValidator();
 				break;
 			case REACHABLE_COMMIT_TIP:
 				requestValidator = new ReachableCommitTipRequestValidator();
 				break;
 			case ANY:
 				requestValidator = new AnyRequestValidator();
 				break;
 		}
 	}
 
 	/**
 	 * @param validator
 	 *            custom validator for client want list.
 	 * @since 3.1
 	 */
 	public void setRequestValidator(RequestValidator validator) {
 		requestValidator = validator != null ? validator
 				: new AdvertisedRequestValidator();
 	}
 
 	/** @return the hook used while advertising the refs to the client */
 	public AdvertiseRefsHook getAdvertiseRefsHook() {
 		return advertiseRefsHook;
 	}
 
 	/** @return the filter used while advertising the refs to the client */
 	public RefFilter getRefFilter() {
 		return refFilter;
 	}
 
 	/**
 	 * Set the hook used while advertising the refs to the client.
 	 * <p>
 	 * If the {@link AdvertiseRefsHook} chooses to call
 	 * {@link #setAdvertisedRefs(Map)}, only refs set by this hook <em>and</em>
 	 * selected by the {@link RefFilter} will be shown to the client.
 	 *
 	 * @param advertiseRefsHook
 	 *            the hook; may be null to show all refs.
 	 */
 	public void setAdvertiseRefsHook(final AdvertiseRefsHook advertiseRefsHook) {
 		if (advertiseRefsHook != null)
 			this.advertiseRefsHook = advertiseRefsHook;
 		else
 			this.advertiseRefsHook = AdvertiseRefsHook.DEFAULT;
 	}
 
 	/**
 	 * Set the filter used while advertising the refs to the client.
 	 * <p>
 	 * Only refs allowed by this filter will be sent to the client.
 	 * The filter is run against the refs specified by the
 	 * {@link AdvertiseRefsHook} (if applicable). If null or not set, uses the
 	 * filter implied by the {@link TransferConfig}.
 	 *
 	 * @param refFilter
 	 *            the filter; may be null to show all refs.
 	 */
 	public void setRefFilter(final RefFilter refFilter) {
 		this.refFilter = refFilter != null ? refFilter : RefFilter.DEFAULT;
 	}
 
 	/** @return the configured upload hook. */
 	public PreUploadHook getPreUploadHook() {
 		return preUploadHook;
 	}
 
 	/**
 	 * Set the hook that controls how this instance will behave.
 	 *
 	 * @param hook
 	 *            the hook; if null no special actions are taken.
 	 */
 	public void setPreUploadHook(PreUploadHook hook) {
 		preUploadHook = hook != null ? hook : PreUploadHook.NULL;
 	}
 
 	/**
 	 * Set the configuration used by the pack generator.
 	 *
 	 * @param pc
 	 *            configuration controlling packing parameters. If null the
 	 *            source repository's settings will be used.
 	 */
 	public void setPackConfig(PackConfig pc) {
 		this.packConfig = pc;
 	}
 
 	/**
 	 * @param tc
 	 *            configuration controlling transfer options. If null the source
 	 *            repository's settings will be used.
 	 * @since 3.1
 	 */
 	public void setTransferConfig(TransferConfig tc) {
 		this.transferConfig = tc != null ? tc : new TransferConfig(db);
 		setRequestPolicy(transferConfig.isAllowTipSha1InWant()
 				? RequestPolicy.TIP : RequestPolicy.ADVERTISED);
 	}
 
 	/** @return the configured logger. */
 	public UploadPackLogger getLogger() {
 		return logger;
 	}
 
 	/**
 	 * Set the logger.
 	 *
 	 * @param logger
 	 *            the logger instance. If null, no logging occurs.
 	 */
 	public void setLogger(UploadPackLogger logger) {
 		this.logger = logger;
 	}
 
 	/**
 	 * Check whether the client expects a side-band stream.
 	 *
 	 * @return true if the client has advertised a side-band capability, false
 	 *     otherwise.
 	 * @throws RequestNotYetReadException
 	 *             if the client's request has not yet been read from the wire, so
 	 *             we do not know if they expect side-band. Note that the client
 	 *             may have already written the request, it just has not been
 	 *             read.
 	 */
 	public boolean isSideBand() throws RequestNotYetReadException {
 		if (options == null)
 			throw new RequestNotYetReadException();
 		return (options.contains(OPTION_SIDE_BAND)
 				|| options.contains(OPTION_SIDE_BAND_64K));
 	}
 
 	/**
 	 * Execute the upload task on the socket.
 	 *
 	 * @param input
 	 *            raw input to read client commands from. Caller must ensure the
 	 *            input is buffered, otherwise read performance may suffer.
 	 * @param output
 	 *            response back to the Git network client, to write the pack
 	 *            data onto. Caller must ensure the output is buffered,
 	 *            otherwise write performance may suffer.
 	 * @param messages
 	 *            secondary "notice" channel to send additional messages out
 	 *            through. When run over SSH this should be tied back to the
 	 *            standard error channel of the command execution. For most
 	 *            other network connections this should be null.
 	 * @throws IOException
 	 */
 	public void upload(final InputStream input, final OutputStream output,
 			final OutputStream messages) throws IOException {
 		try {
 			rawIn = input;
 			rawOut = output;
 			if (messages != null)
 				msgOut = messages;
 
 			if (timeout > 0) {
 				final Thread caller = Thread.currentThread();
 				timer = new InterruptTimer(caller.getName() + "-Timer"); //$NON-NLS-1$
 				TimeoutInputStream i = new TimeoutInputStream(rawIn, timer);
 				TimeoutOutputStream o = new TimeoutOutputStream(rawOut, timer);
 				i.setTimeout(timeout * 1000);
 				o.setTimeout(timeout * 1000);
 				rawIn = i;
 				rawOut = o;
 			}
 
 			pckIn = new PacketLineIn(rawIn);
 			pckOut = new PacketLineOut(rawOut);
 			service();
 		} finally {
 			msgOut = NullOutputStream.INSTANCE;
 			walk.close();
 			if (timer != null) {
 				try {
 					timer.terminate();
 				} finally {
 					timer = null;
 				}
 			}
 		}
 	}
 
 	/**
 	 * Get the PackWriter's statistics if a pack was sent to the client.
 	 *
 	 * @return statistics about pack output, if a pack was sent. Null if no pack
 	 *         was sent, such as during the negotation phase of a smart HTTP
 	 *         connection, or if the client was already up-to-date.
 	 * @since 3.0
 	 */
 	public PackWriter.Statistics getPackStatistics() {
 		return statistics;
 	}
 
 	private Map<String, Ref> getAdvertisedOrDefaultRefs() {
 		if (refs == null)
 			setAdvertisedRefs(null);
 		return refs;
 	}
 
 	private void service() throws IOException {
 		if (biDirectionalPipe)
 			sendAdvertisedRefs(new PacketLineOutRefAdvertiser(pckOut));
 		else if (requestValidator instanceof AnyRequestValidator)
 			advertised = Collections.emptySet();
 		else
 			advertised = refIdSet(getAdvertisedOrDefaultRefs().values());
 
 		boolean sendPack;
 		try {
 			recvWants();
 			if (wantIds.isEmpty()) {
 				preUploadHook.onBeginNegotiateRound(this, wantIds, 0);
 				preUploadHook.onEndNegotiateRound(this, wantIds, 0, 0, false);
 				return;
 			}
 
 			if (options.contains(OPTION_MULTI_ACK_DETAILED)) {
 				multiAck = MultiAck.DETAILED;
 				noDone = options.contains(OPTION_NO_DONE);
 			} else if (options.contains(OPTION_MULTI_ACK))
 				multiAck = MultiAck.CONTINUE;
 			else
 				multiAck = MultiAck.OFF;
 
 			if (depth != 0)
 				processShallow();
 			if (!clientShallowCommits.isEmpty())
 				walk.assumeShallow(clientShallowCommits);
 			sendPack = negotiate();
 		} catch (PackProtocolException err) {
 			reportErrorDuringNegotiate(err.getMessage());
 			throw err;
 
 		} catch (ServiceMayNotContinueException err) {
 			if (!err.isOutput() && err.getMessage() != null) {
 				try {
 					pckOut.writeString("ERR " + err.getMessage() + "\n"); //$NON-NLS-1$ //$NON-NLS-2$
 					err.setOutput();
 				} catch (Throwable err2) {
 					// Ignore this secondary failure (and not mark output).
 				}
 			}
 			throw err;
 
 		} catch (IOException err) {
 			reportErrorDuringNegotiate(JGitText.get().internalServerError);
 			throw err;
 		} catch (RuntimeException err) {
 			reportErrorDuringNegotiate(JGitText.get().internalServerError);
 			throw err;
 		} catch (Error err) {
 			reportErrorDuringNegotiate(JGitText.get().internalServerError);
 			throw err;
 		}
 
 		if (sendPack)
 			sendPack();
 	}
 
 	private static Set<ObjectId> refIdSet(Collection<Ref> refs) {
 		Set<ObjectId> ids = new HashSet<ObjectId>(refs.size());
 		for (Ref ref : refs) {
 			if (ref.getObjectId() != null)
 				ids.add(ref.getObjectId());
 		}
 		return ids;
 	}
 
 	private void reportErrorDuringNegotiate(String msg) {
 		try {
 			pckOut.writeString("ERR " + msg + "\n"); //$NON-NLS-1$ //$NON-NLS-2$
 		} catch (Throwable err) {
 			// Ignore this secondary failure.
 		}
 	}
 
 	private void processShallow() throws IOException {
 		try (DepthWalk.RevWalk depthWalk = new DepthWalk.RevWalk(
 				walk.getObjectReader(), depth)) {
 
 			// Find all the commits which will be shallow
 			for (ObjectId o : wantIds) {
 				try {
 					depthWalk.markRoot(depthWalk.parseCommit(o));
 				} catch (IncorrectObjectTypeException notCommit) {
 					// Ignore non-commits in this loop.
 				}
 			}
 
 			RevCommit o;
 			while ((o = depthWalk.next()) != null) {
 				DepthWalk.Commit c = (DepthWalk.Commit) o;
 
 				// Commits at the boundary which aren't already shallow in
 				// the client need to be marked as such
 				if (c.getDepth() == depth && !clientShallowCommits.contains(c))
 					pckOut.writeString("shallow " + o.name()); //$NON-NLS-1$
 
 				// Commits not on the boundary which are shallow in the client
 				// need to become unshallowed
 				if (c.getDepth() < depth && clientShallowCommits.remove(c)) {
 					unshallowCommits.add(c.copy());
 					pckOut.writeString("unshallow " + c.name()); //$NON-NLS-1$
 				}
 			}
 		}
 		pckOut.end();
 	}
 
 	/**
 	 * Generate an advertisement of available refs and capabilities.
 	 *
 	 * @param adv
 	 *            the advertisement formatter.
 	 * @throws IOException
 	 *             the formatter failed to write an advertisement.
 	 * @throws ServiceMayNotContinueException
 	 *             the hook denied advertisement.
 	 */
 	public void sendAdvertisedRefs(final RefAdvertiser adv) throws IOException,
 			ServiceMayNotContinueException {
 		try {
 			advertiseRefsHook.advertiseRefs(this);
 		} catch (ServiceMayNotContinueException fail) {
 			if (fail.getMessage() != null) {
 				adv.writeOne("ERR " + fail.getMessage()); //$NON-NLS-1$
 				fail.setOutput();
 			}
 			throw fail;
 		}
 
 		adv.init(db);
 		adv.advertiseCapability(OPTION_INCLUDE_TAG);
 		adv.advertiseCapability(OPTION_MULTI_ACK_DETAILED);
 		adv.advertiseCapability(OPTION_MULTI_ACK);
 		adv.advertiseCapability(OPTION_OFS_DELTA);
 		adv.advertiseCapability(OPTION_SIDE_BAND);
 		adv.advertiseCapability(OPTION_SIDE_BAND_64K);
 		adv.advertiseCapability(OPTION_THIN_PACK);
 		adv.advertiseCapability(OPTION_NO_PROGRESS);
 		adv.advertiseCapability(OPTION_SHALLOW);
 		if (!biDirectionalPipe)
 			adv.advertiseCapability(OPTION_NO_DONE);
 		RequestPolicy policy = getRequestPolicy();
 		if (policy == RequestPolicy.TIP
 				|| policy == RequestPolicy.REACHABLE_COMMIT_TIP
 				|| policy == null)
 			adv.advertiseCapability(OPTION_ALLOW_TIP_SHA1_IN_WANT);
 		adv.advertiseCapability(OPTION_AGENT, UserAgent.get());
 		adv.setDerefTags(true);
 		Map<String, Ref> advertisedOrDefaultRefs = getAdvertisedOrDefaultRefs();
 		findSymrefs(adv, advertisedOrDefaultRefs);
 		advertised = adv.send(advertisedOrDefaultRefs);
 		if (adv.isEmpty())
 			adv.advertiseId(ObjectId.zeroId(), "capabilities^{}"); //$NON-NLS-1$
 		adv.end();
 	}
 
 	/**
 	 * Send a message to the client, if it supports receiving them.
 	 * <p>
 	 * If the client doesn't support receiving messages, the message will be
 	 * discarded, with no other indication to the caller or to the client.
 	 *
 	 * @param what
 	 *            string describing the problem identified by the hook. The
 	 *            string must not end with an LF, and must not contain an LF.
 	 * @since 3.1
 	 */
 	public void sendMessage(String what) {
 		try {
 			msgOut.write(Constants.encode(what + "\n")); //$NON-NLS-1$
 		} catch (IOException e) {
 			// Ignore write failures.
 		}
 	}
 
 	/**
 	 * @return an underlying stream for sending messages to the client, or null.
 	 * @since 3.1
 	 */
 	public OutputStream getMessageOutputStream() {
 		return msgOut;
 	}
 
 	private void recvWants() throws IOException {
 		boolean isFirst = true;
 		for (;;) {
 			String line;
 			try {
 				line = pckIn.readString();
 			} catch (EOFException eof) {
 				if (isFirst)
 					break;
 				throw eof;
 			}
 
 			if (line == PacketLineIn.END)
 				break;
 
 			if (line.startsWith("deepen ")) { //$NON-NLS-1$
 				depth = Integer.parseInt(line.substring(7));
 				continue;
 			}
 
 			if (line.startsWith("shallow ")) { //$NON-NLS-1$
 				clientShallowCommits.add(ObjectId.fromString(line.substring(8)));
 				continue;
 			}
 
 			if (!line.startsWith("want ") || line.length() < 45) //$NON-NLS-1$
 				throw new PackProtocolException(MessageFormat.format(JGitText.get().expectedGot, "want", line)); //$NON-NLS-1$
 
 			if (isFirst) {
 				if (line.length() > 45) {
 					FirstLine firstLine = new FirstLine(line);
 					options = firstLine.getOptions();
 					line = firstLine.getLine();
 				} else
 					options = Collections.emptySet();
 			}
 
 			wantIds.add(ObjectId.fromString(line.substring(5)));
 			isFirst = false;
 		}
 	}
 
 	/**
 	 * Returns the clone/fetch depth. Valid only after calling recvWants().
 	 *
 	 * @return the depth requested by the client, or 0 if unbounded.
 	 * @since 4.0
 	 */
 	public int getDepth() {
 		if (options == null)
 			throw new RequestNotYetReadException();
 		return depth;
 	}
 
 	/**
 	 * Get the user agent of the client.
 	 * <p>
 	 * If the client is new enough to use {@code agent=} capability that value
 	 * will be returned. Older HTTP clients may also supply their version using
 	 * the HTTP {@code User-Agent} header. The capability overrides the HTTP
 	 * header if both are available.
 	 * <p>
 	 * When an HTTP request has been received this method returns the HTTP
 	 * {@code User-Agent} header value until capabilities have been parsed.
 	 *
 	 * @return user agent supplied by the client. Available only if the client
 	 *         is new enough to advertise its user agent.
 	 * @since 4.0
 	 */
 	public String getPeerUserAgent() {
 		return UserAgent.getAgent(options, userAgent);
 	}
 
 	private boolean negotiate() throws IOException {
 		okToGiveUp = Boolean.FALSE;
 
 		ObjectId last = ObjectId.zeroId();
 		List<ObjectId> peerHas = new ArrayList<ObjectId>(64);
 		for (;;) {
 			String line;
 			try {
 				line = pckIn.readString();
 			} catch (EOFException eof) {
 				// EOF on stateless RPC (aka smart HTTP) and non-shallow request
 				// means the client asked for the updated shallow/unshallow data,
 				// disconnected, and will try another request with actual want/have.
 				// Don't report the EOF here, its a bug in the protocol that the client
 				// just disconnects without sending an END.
 				if (!biDirectionalPipe && depth > 0)
 					return false;
 				throw eof;
 			}
 
 			if (line == PacketLineIn.END) {
 				last = processHaveLines(peerHas, last);
 				if (commonBase.isEmpty() || multiAck != MultiAck.OFF)
 					pckOut.writeString("NAK\n"); //$NON-NLS-1$
 				if (noDone && sentReady) {
 					pckOut.writeString("ACK " + last.name() + "\n"); //$NON-NLS-1$ //$NON-NLS-2$
 					return true;
 				}
 				if (!biDirectionalPipe)
 					return false;
 				pckOut.flush();
 
 			} else if (line.startsWith("have ") && line.length() == 45) { //$NON-NLS-1$
 				peerHas.add(ObjectId.fromString(line.substring(5)));
 
 			} else if (line.equals("done")) { //$NON-NLS-1$
 				last = processHaveLines(peerHas, last);
 
 				if (commonBase.isEmpty())
 					pckOut.writeString("NAK\n"); //$NON-NLS-1$
 
 				else if (multiAck != MultiAck.OFF)
 					pckOut.writeString("ACK " + last.name() + "\n"); //$NON-NLS-1$ //$NON-NLS-2$
 
 				return true;
 
 			} else {
 				throw new PackProtocolException(MessageFormat.format(JGitText.get().expectedGot, "have", line)); //$NON-NLS-1$
 			}
 		}
 	}
 
 	private ObjectId processHaveLines(List<ObjectId> peerHas, ObjectId last)
 			throws IOException {
 		preUploadHook.onBeginNegotiateRound(this, wantIds, peerHas.size());
 		if (wantAll.isEmpty() && !wantIds.isEmpty())
 			parseWants();
 		if (peerHas.isEmpty())
 			return last;
 
 		sentReady = false;
 		int haveCnt = 0;
 		walk.getObjectReader().setAvoidUnreachableObjects(true);
 		AsyncRevObjectQueue q = walk.parseAny(peerHas, false);
 		try {
 			for (;;) {
 				RevObject obj;
 				try {
 					obj = q.next();
 				} catch (MissingObjectException notFound) {
 					continue;
 				}
 				if (obj == null)
 					break;
 
 				last = obj;
 				haveCnt++;
 
 				if (obj instanceof RevCommit) {
 					RevCommit c = (RevCommit) obj;
 					if (oldestTime == 0 || c.getCommitTime() < oldestTime)
 						oldestTime = c.getCommitTime();
 				}
 
 				if (obj.has(PEER_HAS))
 					continue;
 
 				obj.add(PEER_HAS);
 				if (obj instanceof RevCommit)
 					((RevCommit) obj).carry(PEER_HAS);
 				addCommonBase(obj);
 
 				// If both sides have the same object; let the client know.
 				//
 				switch (multiAck) {
 				case OFF:
 					if (commonBase.size() == 1)
 						pckOut.writeString("ACK " + obj.name() + "\n"); //$NON-NLS-1$ //$NON-NLS-2$
 					break;
 				case CONTINUE:
 					pckOut.writeString("ACK " + obj.name() + " continue\n"); //$NON-NLS-1$ //$NON-NLS-2$
 					break;
 				case DETAILED:
 					pckOut.writeString("ACK " + obj.name() + " common\n"); //$NON-NLS-1$ //$NON-NLS-2$
 					break;
 				}
 			}
 		} finally {
 			q.release();
 			walk.getObjectReader().setAvoidUnreachableObjects(false);
 		}
 
 		int missCnt = peerHas.size() - haveCnt;
 
 		// If we don't have one of the objects but we're also willing to
 		// create a pack at this point, let the client know so it stops
 		// telling us about its history.
 		//
 		boolean didOkToGiveUp = false;
 		if (0 < missCnt) {
 			for (int i = peerHas.size() - 1; i >= 0; i--) {
 				ObjectId id = peerHas.get(i);
 				if (walk.lookupOrNull(id) == null) {
 					didOkToGiveUp = true;
 					if (okToGiveUp()) {
 						switch (multiAck) {
 						case OFF:
 							break;
 						case CONTINUE:
 							pckOut.writeString("ACK " + id.name() + " continue\n"); //$NON-NLS-1$ //$NON-NLS-2$
 							break;
 						case DETAILED:
 							pckOut.writeString("ACK " + id.name() + " ready\n"); //$NON-NLS-1$ //$NON-NLS-2$
 							sentReady = true;
 							break;
 						}
 					}
 					break;
 				}
 			}
 		}
 
 		if (multiAck == MultiAck.DETAILED && !didOkToGiveUp && okToGiveUp()) {
 			ObjectId id = peerHas.get(peerHas.size() - 1);
 			sentReady = true;
 			pckOut.writeString("ACK " + id.name() + " ready\n"); //$NON-NLS-1$ //$NON-NLS-2$
 			sentReady = true;
 		}
 
 		preUploadHook.onEndNegotiateRound(this, wantAll, haveCnt, missCnt, sentReady);
 		peerHas.clear();
 		return last;
 	}
 
 	private void parseWants() throws IOException {
 		List<ObjectId> notAdvertisedWants = null;
 		for (ObjectId obj : wantIds) {
 			if (!advertised.contains(obj)) {
 				if (notAdvertisedWants == null)
 					notAdvertisedWants = new ArrayList<ObjectId>();
 				notAdvertisedWants.add(obj);
 			}
 		}
 		if (notAdvertisedWants != null)
 			requestValidator.checkWants(this, notAdvertisedWants);
 
 		AsyncRevObjectQueue q = walk.parseAny(wantIds, true);
 		try {
 			RevObject obj;
 			while ((obj = q.next()) != null) {
 				want(obj);
 
 				if (!(obj instanceof RevCommit))
 					obj.add(SATISFIED);
 				if (obj instanceof RevTag) {
 					obj = walk.peel(obj);
 					if (obj instanceof RevCommit)
 						want(obj);
 				}
 			}
 			wantIds.clear();
 		} catch (MissingObjectException notFound) {
 			ObjectId id = notFound.getObjectId();
 			throw new PackProtocolException(MessageFormat.format(
 					JGitText.get().wantNotValid, id.name()), notFound);
 		} finally {
 			q.release();
 		}
 	}
 
 	private void want(RevObject obj) {
 		if (!obj.has(WANT)) {
 			obj.add(WANT);
 			wantAll.add(obj);
 		}
 	}
 
 	/**
 	 * Validator corresponding to {@link RequestPolicy#ADVERTISED}.
 	 *
 	 * @since 3.1
 	 */
 	public static final class AdvertisedRequestValidator
 			implements RequestValidator {
 		public void checkWants(UploadPack up, List<ObjectId> wants)
 				throws PackProtocolException, IOException {
 			if (!up.isBiDirectionalPipe())
 				new ReachableCommitRequestValidator().checkWants(up, wants);
 			else if (!wants.isEmpty())
 				throw new PackProtocolException(MessageFormat.format(
 						JGitText.get().wantNotValid, wants.iterator().next().name()));
 		}
 	}
 
 	/**
 	 * Validator corresponding to {@link RequestPolicy#REACHABLE_COMMIT}.
 	 *
 	 * @since 3.1
 	 */
 	public static final class ReachableCommitRequestValidator
 			implements RequestValidator {
 		public void checkWants(UploadPack up, List<ObjectId> wants)
 				throws PackProtocolException, IOException {
 			checkNotAdvertisedWants(up.getRevWalk(), wants,
 					refIdSet(up.getAdvertisedRefs().values()));
 		}
 	}
 
 	/**
 	 * Validator corresponding to {@link RequestPolicy#TIP}.
 	 *
 	 * @since 3.1
 	 */
 	public static final class TipRequestValidator implements RequestValidator {
 		public void checkWants(UploadPack up, List<ObjectId> wants)
 				throws PackProtocolException, IOException {
 			if (!up.isBiDirectionalPipe())
 				new ReachableCommitTipRequestValidator().checkWants(up, wants);
 			else if (!wants.isEmpty()) {
 				Set<ObjectId> refIds =
 					refIdSet(up.getRepository().getRefDatabase().getRefs(ALL).values());
 				for (ObjectId obj : wants) {
 					if (!refIds.contains(obj))
 						throw new PackProtocolException(MessageFormat.format(
 								JGitText.get().wantNotValid, obj.name()));
 				}
 			}
 		}
 	}
 
 	/**
 	 * Validator corresponding to {@link RequestPolicy#REACHABLE_COMMIT_TIP}.
 	 *
 	 * @since 3.1
 	 */
 	public static final class ReachableCommitTipRequestValidator
 			implements RequestValidator {
 		public void checkWants(UploadPack up, List<ObjectId> wants)
 				throws PackProtocolException, IOException {
 			checkNotAdvertisedWants(up.getRevWalk(), wants,
 					refIdSet(up.getRepository().getRefDatabase().getRefs(ALL).values()));
 		}
 	}
 
 	/**
 	 * Validator corresponding to {@link RequestPolicy#ANY}.
 	 *
 	 * @since 3.1
 	 */
 	public static final class AnyRequestValidator implements RequestValidator {
 		public void checkWants(UploadPack up, List<ObjectId> wants)
 				throws PackProtocolException, IOException {
 			// All requests are valid.
 		}
 	}
 
 	private static void checkNotAdvertisedWants(RevWalk walk,
 			List<ObjectId> notAdvertisedWants, Set<ObjectId> reachableFrom)
 			throws MissingObjectException, IncorrectObjectTypeException, IOException {
 		// Walk the requested commits back to the provided set of commits. If any
 		// commit exists, a branch was deleted or rewound and the repository owner
 		// no longer exports that requested item. If the requested commit is merged
 		// into an advertised branch it will be marked UNINTERESTING and no commits
 		// return.
 
 		AsyncRevObjectQueue q = walk.parseAny(notAdvertisedWants, true);
 		try {
 			RevObject obj;
 			while ((obj = q.next()) != null) {
 				if (!(obj instanceof RevCommit))
 					throw new PackProtocolException(MessageFormat.format(
 						JGitText.get().wantNotValid, obj.name()));
 				walk.markStart((RevCommit) obj);
 			}
 		} catch (MissingObjectException notFound) {
 			ObjectId id = notFound.getObjectId();
 			throw new PackProtocolException(MessageFormat.format(
 					JGitText.get().wantNotValid, id.name()), notFound);
 		} finally {
 			q.release();
 		}
 		for (ObjectId id : reachableFrom) {
 			try {
 				walk.markUninteresting(walk.parseCommit(id));
 			} catch (IncorrectObjectTypeException notCommit) {
 				continue;
 			}
 		}
 
 		RevCommit bad = walk.next();
 		if (bad != null) {
 			throw new PackProtocolException(MessageFormat.format(
 					JGitText.get().wantNotValid,
 					bad.name()));
 		}
 		walk.reset();
 	}
 
 	private void addCommonBase(final RevObject o) {
 		if (!o.has(COMMON)) {
 			o.add(COMMON);
 			commonBase.add(o);
 			okToGiveUp = null;
 		}
 	}
 
 	private boolean okToGiveUp() throws PackProtocolException {
 		if (okToGiveUp == null)
 			okToGiveUp = Boolean.valueOf(okToGiveUpImp());
 		return okToGiveUp.booleanValue();
 	}
 
 	private boolean okToGiveUpImp() throws PackProtocolException {
 		if (commonBase.isEmpty())
 			return false;
 
 		try {
 			for (RevObject obj : wantAll) {
 				if (!wantSatisfied(obj))
 					return false;
 			}
 			return true;
 		} catch (IOException e) {
 			throw new PackProtocolException(JGitText.get().internalRevisionError, e);
 		}
 	}
 
 	private boolean wantSatisfied(final RevObject want) throws IOException {
 		if (want.has(SATISFIED))
 			return true;
 
 		walk.resetRetain(SAVE);
 		walk.markStart((RevCommit) want);
 		if (oldestTime != 0)
 			walk.setRevFilter(CommitTimeRevFilter.after(oldestTime * 1000L));
 		for (;;) {
 			final RevCommit c = walk.next();
 			if (c == null)
 				break;
 			if (c.has(PEER_HAS)) {
 				addCommonBase(c);
 				want.add(SATISFIED);
 				return true;
 			}
 		}
 		return false;
 	}
 
 	private void sendPack() throws IOException {
 		final boolean sideband = options.contains(OPTION_SIDE_BAND)
 				|| options.contains(OPTION_SIDE_BAND_64K);
 
 		if (!biDirectionalPipe) {
 			// Ensure the request was fully consumed. Any remaining input must
 			// be a protocol error. If we aren't at EOF the implementation is broken.
 			int eof = rawIn.read();
 			if (0 <= eof)
 				throw new CorruptObjectException(MessageFormat.format(
 						JGitText.get().expectedEOFReceived,
 						"\\x" + Integer.toHexString(eof))); //$NON-NLS-1$
 		}
 
 		if (sideband) {
 			try {
 				sendPack(true);
 			} catch (ServiceMayNotContinueException noPack) {
 				// This was already reported on (below).
 				throw noPack;
 			} catch (IOException err) {
 				if (reportInternalServerErrorOverSideband())
 					throw new UploadPackInternalServerErrorException(err);
 				else
 					throw err;
 			} catch (RuntimeException err) {
 				if (reportInternalServerErrorOverSideband())
 					throw new UploadPackInternalServerErrorException(err);
 				else
 					throw err;
 			} catch (Error err) {
 				if (reportInternalServerErrorOverSideband())
 					throw new UploadPackInternalServerErrorException(err);
 				else
 					throw err;
 			}
 		} else {
 			sendPack(false);
 		}
 	}
 
 	private boolean reportInternalServerErrorOverSideband() {
 		try {
 			@SuppressWarnings("resource" /* java 7 */)
 			SideBandOutputStream err = new SideBandOutputStream(
 					SideBandOutputStream.CH_ERROR,
 					SideBandOutputStream.SMALL_BUF,
 					rawOut);
 			err.write(Constants.encode(JGitText.get().internalServerError));
 			err.flush();
 			return true;
 		} catch (Throwable cannotReport) {
 			// Ignore the reason. This is a secondary failure.
 			return false;
 		}
 	}
 
 	private void sendPack(final boolean sideband) throws IOException {
 		ProgressMonitor pm = NullProgressMonitor.INSTANCE;
 		OutputStream packOut = rawOut;
 
 		if (sideband) {
 			int bufsz = SideBandOutputStream.SMALL_BUF;
 			if (options.contains(OPTION_SIDE_BAND_64K))
 				bufsz = SideBandOutputStream.MAX_BUF;
 
 			packOut = new SideBandOutputStream(SideBandOutputStream.CH_DATA,
 					bufsz, rawOut);
 			if (!options.contains(OPTION_NO_PROGRESS)) {
 				msgOut = new SideBandOutputStream(
 						SideBandOutputStream.CH_PROGRESS, bufsz, rawOut);
 				pm = new SideBandProgressMonitor(msgOut);
 			}
 		}
 
 		try {
 			if (wantAll.isEmpty()) {
 				preUploadHook.onSendPack(this, wantIds, commonBase);
 			} else {
 				preUploadHook.onSendPack(this, wantAll, commonBase);
 			}
 			msgOut.flush();
 		} catch (ServiceMayNotContinueException noPack) {
 			if (sideband && noPack.getMessage() != null) {
 				noPack.setOutput();
 				@SuppressWarnings("resource" /* java 7 */)
 				SideBandOutputStream err = new SideBandOutputStream(
 						SideBandOutputStream.CH_ERROR,
 						SideBandOutputStream.SMALL_BUF, rawOut);
 				err.write(Constants.encode(noPack.getMessage()));
 				err.flush();
 			}
 			throw noPack;
 		}
 
 		PackConfig cfg = packConfig;
 		if (cfg == null)
 			cfg = new PackConfig(db);
 		final PackWriter pw = new PackWriter(cfg, walk.getObjectReader());
 		try {
 			pw.setIndexDisabled(true);
 			pw.setUseCachedPacks(true);
 			pw.setUseBitmaps(depth == 0 && clientShallowCommits.isEmpty());
 			pw.setReuseDeltaCommits(true);
 			pw.setDeltaBaseAsOffset(options.contains(OPTION_OFS_DELTA));
 			pw.setThin(options.contains(OPTION_THIN_PACK));
 			pw.setReuseValidatingObjects(false);
 
 			if (commonBase.isEmpty() && refs != null) {
 				Set<ObjectId> tagTargets = new HashSet<ObjectId>();
 				for (Ref ref : refs.values()) {
 					if (ref.getPeeledObjectId() != null)
 						tagTargets.add(ref.getPeeledObjectId());
 					else if (ref.getObjectId() == null)
 						continue;
 					else if (ref.getName().startsWith(Constants.R_HEADS))
 						tagTargets.add(ref.getObjectId());
 				}
 				pw.setTagTargets(tagTargets);
 			}
 
 			if (depth > 0)
 				pw.setShallowPack(depth, unshallowCommits);
 
 			RevWalk rw = walk;
 			if (wantAll.isEmpty()) {
 				pw.preparePack(pm, wantIds, commonBase);
 			} else {
 				walk.reset();
 
 				ObjectWalk ow = walk.toObjectWalkWithSameObjects();
 				pw.preparePack(pm, ow, wantAll, commonBase);
 				rw = ow;
 			}
 
 			if (options.contains(OPTION_INCLUDE_TAG) && refs != null) {
 				for (Ref ref : refs.values()) {
 					ObjectId objectId = ref.getObjectId();
 
 					// If the object was already requested, skip it.
 					if (wantAll.isEmpty()) {
 						if (wantIds.contains(objectId))
 							continue;
 					} else {
 						RevObject obj = rw.lookupOrNull(objectId);
 						if (obj != null && obj.has(WANT))
 							continue;
 					}
 
 					if (!ref.isPeeled())
 						ref = db.peel(ref);
 
 					ObjectId peeledId = ref.getPeeledObjectId();
 					if (peeledId == null)
 						continue;
 
 					objectId = ref.getObjectId();
 					if (pw.willInclude(peeledId) && !pw.willInclude(objectId))
 						pw.addObject(rw.parseAny(objectId));
 				}
 			}
 
 			pw.writePack(pm, NullProgressMonitor.INSTANCE, packOut);
 
 			if (msgOut != NullOutputStream.INSTANCE) {
 				String msg = pw.getStatistics().getMessage() + '\n';
 				msgOut.write(Constants.encode(msg));
 				msgOut.flush();
 			}
 
 		} finally {
 			statistics = pw.getStatistics();
 			if (statistics != null)
 				logger.onPackStatistics(statistics);
 			pw.close();
 		}
 
 		if (sideband)
 			pckOut.end();
 	}
 
 	private static void findSymrefs(
 			final RefAdvertiser adv, final Map<String, Ref> refs) {
 		Ref head = refs.get(Constants.HEAD);
 		if (head != null && head.isSymbolic()) {
 			adv.addSymref(Constants.HEAD, head.getLeaf().getName());
 		}
 	}
 }