/*
 * 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 java.util.Collections.unmodifiableMap;
import static org.eclipse.jgit.lib.Constants.R_TAGS;
import static org.eclipse.jgit.transport.GitProtocolConstants.CAPABILITY_REF_IN_WANT;
import static org.eclipse.jgit.transport.GitProtocolConstants.CAPABILITY_SERVER_OPTION;
import static org.eclipse.jgit.transport.GitProtocolConstants.COMMAND_FETCH;
import static org.eclipse.jgit.transport.GitProtocolConstants.COMMAND_LS_REFS;
import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_AGENT;
import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_ALLOW_REACHABLE_SHA1_IN_WANT;
import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_ALLOW_TIP_SHA1_IN_WANT;
import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_DEEPEN_RELATIVE;
import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_FILTER;
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_SIDEBAND_ALL;
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 static org.eclipse.jgit.util.RefMap.toRefMap;

import java.io.ByteArrayOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.UncheckedIOException;
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.Objects;
import java.util.Optional;
import java.util.Set;
import java.util.TreeMap;
import java.util.stream.Collectors;

import org.eclipse.jgit.annotations.NonNull;
import org.eclipse.jgit.annotations.Nullable;
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.CachedPackUriProvider;
import org.eclipse.jgit.internal.storage.pack.PackWriter;
import org.eclipse.jgit.internal.transport.parser.FirstWant;
import org.eclipse.jgit.lib.BitmapIndex;
import org.eclipse.jgit.lib.BitmapIndex.BitmapBuilder;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.NullProgressMonitor;
import org.eclipse.jgit.lib.ObjectId;
import org.eclipse.jgit.lib.ObjectReader;
import org.eclipse.jgit.lib.ProgressMonitor;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.RefDatabase;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.AsyncRevObjectQueue;
import org.eclipse.jgit.revwalk.BitmapWalker;
import org.eclipse.jgit.revwalk.DepthWalk;
import org.eclipse.jgit.revwalk.ObjectWalk;
import org.eclipse.jgit.revwalk.ReachabilityChecker;
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.RevSort;
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.storage.pack.PackStatistics;
import org.eclipse.jgit.transport.GitProtocolConstants.MultiAck;
import org.eclipse.jgit.transport.RefAdvertiser.PacketLineOutRefAdvertiser;
import org.eclipse.jgit.transport.TransferConfig.ProtocolVersion;
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.
/**
 * Implements the server side of a fetch connection, transmitting objects.
 */
public class UploadPack {
	
Policy the server uses to validate client requests /** Policy the server uses to validate client requests */
	public static enum RequestPolicy {
		
Client may only ask for objects the server advertised a reference for. /** 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.
/**
		 * 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.
 This may happen, for example, when a custom RefFilter is set. 
Since:
3.1/**
		 * 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/**
		 * 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. /** Client may ask for any SHA-1 in the repository. */
		ANY;
	}

	
Validator for client requests.
Since:
3.1/**
	 * Validator for client requests.
	 *
	 * @since 3.1
	 */
	public interface RequestValidator {
		
Check a list of client wants against the request policy.
Params:
up –  UploadPack instance.
wants – 
           objects the client requested that were not advertised.
Throws:
PackProtocolException – 
           if one or more wants is not valid.
IOException – 
           if a low-level exception occurred.
Since:
3.1/**
		 * 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 want-list, the line itself plus options.
Deprecated:
Use FirstWant instead/**
	 * Data in the first line of a want-list, the line itself plus options.
	 *
	 * @deprecated Use {@link FirstWant} instead
	 */
	@Deprecated
	public static class FirstLine {

		private final FirstWant firstWant;

		
Params:
line – 
           line from the client./**
		 * @param line
		 *            line from the client.
		 */
		public FirstLine(String line) {
			try {
				firstWant = FirstWant.fromLine(line);
			} catch (PackProtocolException e) {
				throw new UncheckedIOException(e);
			}
		}

		
Returns:
non-capabilities part of the line./** @return non-capabilities part of the line. */
		public String getLine() {
			return firstWant.getLine();
		}

		
Returns:
capabilities parsed from the line./** @return capabilities parsed from the line. */
		public Set<String> getOptions() {
			if (firstWant.getAgent() != null) {
				Set<String> caps = new HashSet<>(firstWant.getCapabilities());
				caps.add(OPTION_AGENT + '=' + firstWant.getAgent());
				return caps;
			}
			return firstWant.getCapabilities();
		}
	}

	/*
	 * {@link java.util.function.Consumer} doesn't allow throwing checked
	 * exceptions. Define our own to propagate IOExceptions.
	 */
	@FunctionalInterface
	private static interface IOConsumer<R> {
		void accept(R t) throws IOException;
	}

	
Database we read the objects from. /** Database we read the objects from. */
	private final Repository db;

	
Revision traversal support over db. /** Revision traversal support over {@link #db}. */
	private final RevWalk walk;

	
Configuration to pass into the PackWriter. /** Configuration to pass into the PackWriter. */
	private PackConfig packConfig;

	
Configuration for various transfer options. /** Configuration for various transfer options. */
	private TransferConfig transferConfig;

	
Timeout in seconds to wait for client interaction. /** Timeout in seconds to wait for client interaction. */
	private int timeout;

	
Is the client connection a bi-directional socket or pipe?

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.

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.
/**
	 * 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 timeout. /** Timer to manage {@link #timeout}. */
	private InterruptTimer timer;

	
Whether the client requested to use protocol V2 through a side
channel (such as the Git-Protocol HTTP header).
/**
	 * Whether the client requested to use protocol V2 through a side
	 * channel (such as the Git-Protocol HTTP header).
	 */
	private boolean clientRequestedV2;

	private InputStream rawIn;

	private ResponseBufferedOutputStream rawOut;

	private PacketLineIn pckIn;

	private OutputStream msgOut = NullOutputStream.INSTANCE;

	
Refs eligible for advertising to the client, set using setAdvertisedRefs. /**
	 * Refs eligible for advertising to the client, set using
	 * {@link #setAdvertisedRefs}.
	 */
	private Map<String, Ref> refs;

	
Hook used while processing Git protocol v2 requests. /** Hook used while processing Git protocol v2 requests. */
	private ProtocolV2Hook protocolV2Hook = ProtocolV2Hook.DEFAULT;

	
Hook used while advertising the refs to the client. /** Hook used while advertising the refs to the client. */
	private AdvertiseRefsHook advertiseRefsHook = AdvertiseRefsHook.DEFAULT;

	
Whether the advertiseRefsHook has been invoked. /** Whether the {@link #advertiseRefsHook} has been invoked. */
	private boolean advertiseRefsHookCalled;

	
Filter used while advertising the refs to the client. /** Filter used while advertising the refs to the client. */
	private RefFilter refFilter = RefFilter.DEFAULT;

	
Hook handling the various upload phases. /** Hook handling the various upload phases. */
	private PreUploadHook preUploadHook = PreUploadHook.NULL;

	
Hook for taking post upload actions. /** Hook for taking post upload actions. */
	private PostUploadHook postUploadHook = PostUploadHook.NULL;

	
Caller user agent /** Caller user agent */
	String userAgent;

	
Raw ObjectIds the client has asked for, before validating them. /** Raw ObjectIds the client has asked for, before validating them. */
	private Set<ObjectId> wantIds = new HashSet<>();

	
Objects the client wants to obtain. /** Objects the client wants to obtain. */
	private final Set<RevObject> wantAll = new HashSet<>();

	
Objects on both sides, these don't have to be sent. /** Objects on both sides, these don't have to be sent. */
	private final Set<RevObject> commonBase = new HashSet<>();

	
Commit time of the oldest common commit, in seconds. /** Commit time of the oldest common commit, in seconds. */
	private int oldestTime;

	
null if commonBase should be examined again. /** 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. /** 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. /** Marked on objects the client has asked us to give them. */
	private final RevFlag WANT;

	
Marked on objects both we and the client have. /** Marked on objects both we and the client have. */
	private final RevFlag PEER_HAS;

	
Marked on objects in commonBase. /** Marked on objects in {@link #commonBase}. */
	private final RevFlag COMMON;

	
Objects where we found a path from the want list to a common base. /** 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 PackStatistics statistics;

	
Request this instance is handling. We need to keep a reference to it for pre upload
hooks. They receive a reference this instance and invoke methods like getDepth() to get information about the request. /**
	 * Request this instance is handling.
	 *
	 * We need to keep a reference to it for {@link PreUploadHook pre upload
	 * hooks}. They receive a reference this instance and invoke methods like
	 * getDepth() to get information about the request.
	 */
	private FetchRequest currentRequest;

	private CachedPackUriProvider cachedPackUriProvider;

	
Create a new pack upload for an open repository.
Params:
copyFrom – 
           the source repository./**
	 * Create a new pack upload for an open repository.
	 *
	 * @param copyFrom
	 *            the source repository.
	 */
	public UploadPack(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);
	}

	
Get the repository this upload is reading from.
Returns:
the repository this upload is reading from./**
	 * Get the repository this upload is reading from.
	 *
	 * @return the repository this upload is reading from.
	 */
	public final Repository getRepository() {
		return db;
	}

	
Get the RevWalk instance used by this connection.
Returns:
the RevWalk instance used by this connection./**
	 * Get the RevWalk instance used by this connection.
	 *
	 * @return the RevWalk instance used by this connection.
	 */
	public final RevWalk getRevWalk() {
		return walk;
	}

	
Get refs which were advertised to the client.
Returns:
all refs which were advertised to the client, or null if setAdvertisedRefs(Map<String,Ref>) has not been called yet./**
	 * 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.
 Intended to be called from a PreUploadHook. 
Params:
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 getRefFilter(). If null, assumes all refs were advertised./**
	 * Set the refs advertised by this UploadPack.
	 * <p>
	 * Intended to be called from a
	 * {@link org.eclipse.jgit.transport.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(@Nullable 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);
	}

	
Get timeout (in seconds) before aborting an IO operation.
Returns:
timeout (in seconds) before aborting an IO operation./**
	 * Get timeout (in seconds) before aborting an IO operation.
	 *
	 * @return timeout (in seconds) before aborting an IO operation.
	 */
	public int getTimeout() {
		return timeout;
	}

	
Set the timeout before willing to abort an IO call.
Params:
seconds – 
           number of seconds to wait (with no data transfer occurring)
           before aborting an IO read or write operation with the
           connected client./**
	 * 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(int seconds) {
		timeout = seconds;
	}

	
Whether this class expects a bi-directional pipe opened between the
client and itself.
Returns:
true if this class expects a bi-directional pipe opened between
        the client and itself. The default is true./**
	 * Whether this class expects a bi-directional pipe opened between the
	 * client and itself.
	 *
	 * @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;
	}

	
Set whether this class will assume the socket is a fully bidirectional
pipe between the two peers
Params:
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./**
	 * Set whether this class will assume the socket is a fully bidirectional
	 * pipe between the two peers
	 *
	 * @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(boolean twoWay) {
		biDirectionalPipe = twoWay;
	}

	
Get policy used by the service to validate client requests
Returns:
policy used by the service to validate client requests, or null
        for a custom request validator./**
	 * Get policy used by the service to validate client requests
	 *
	 * @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;
	}

	
Set the policy used to enforce validation of a client's want list.
Params:
policy –  the policy used to enforce validation of a client's want list. By default the policy is 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 RequestPolicy.REACHABLE_COMMIT or RequestPolicy.REACHABLE_COMMIT_TIP when callers have setBiDirectionalPipe(boolean) set to false. Overrides any policy specified in a TransferConfig./**
	 * Set the policy used to enforce validation of a client's want list.
	 *
	 * @param policy
	 *            the policy used to enforce validation of a client's want list.
	 *            By default the policy is
	 *            {@link org.eclipse.jgit.transport.UploadPack.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 org.eclipse.jgit.transport.UploadPack.RequestPolicy#REACHABLE_COMMIT}
	 *            or
	 *            {@link org.eclipse.jgit.transport.UploadPack.RequestPolicy#REACHABLE_COMMIT_TIP}
	 *            when callers have {@link #setBiDirectionalPipe(boolean)} set
	 *            to false. Overrides any policy specified in a
	 *            {@link org.eclipse.jgit.transport.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;
		}
	}

	
Set custom validator for client want list.
Params:
validator – 
           custom validator for client want list.
Since:
3.1/**
	 * Set custom validator for client want list.
	 *
	 * @param validator
	 *            custom validator for client want list.
	 * @since 3.1
	 */
	public void setRequestValidator(@Nullable RequestValidator validator) {
		requestValidator = validator != null ? validator
				: new AdvertisedRequestValidator();
	}

	
Get the hook used while advertising the refs to the client.
Returns:
the hook used while advertising the refs to the client./**
	 * Get the hook used while advertising the refs to the client.
	 *
	 * @return the hook used while advertising the refs to the client.
	 */
	public AdvertiseRefsHook getAdvertiseRefsHook() {
		return advertiseRefsHook;
	}

	
Get the filter used while advertising the refs to the client.
Returns:
the filter used while advertising the refs to the client./**
	 * Get the filter used while advertising the refs to the client.
	 *
	 * @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.
 If the AdvertiseRefsHook chooses to call setAdvertisedRefs(Map<String,Ref>), only refs set by this hook and selected by the RefFilter will be shown to the client. 
Params:
advertiseRefsHook – 
           the hook; may be null to show all refs./**
	 * Set the hook used while advertising the refs to the client.
	 * <p>
	 * If the {@link org.eclipse.jgit.transport.AdvertiseRefsHook} chooses to
	 * call {@link #setAdvertisedRefs(Map)}, only refs set by this hook
	 * <em>and</em> selected by the {@link org.eclipse.jgit.transport.RefFilter}
	 * will be shown to the client.
	 *
	 * @param advertiseRefsHook
	 *            the hook; may be null to show all refs.
	 */
	public void setAdvertiseRefsHook(
			@Nullable AdvertiseRefsHook advertiseRefsHook) {
		this.advertiseRefsHook = advertiseRefsHook != null ? advertiseRefsHook
				: AdvertiseRefsHook.DEFAULT;
	}

	
Set the protocol V2 hook.
Params:
hook – 
           the hook; if null no special actions are taken.
Since:
5.1/**
	 * Set the protocol V2 hook.
	 *
	 * @param hook
	 *            the hook; if null no special actions are taken.
	 * @since 5.1
	 */
	public void setProtocolV2Hook(@Nullable ProtocolV2Hook hook) {
		this.protocolV2Hook = hook != null ? hook : ProtocolV2Hook.DEFAULT;
	}

	
Get the currently installed protocol v2 hook.
Returns:
the hook or a default implementation if none installed.
Since:
5.5/**
	 * Get the currently installed protocol v2 hook.
	 *
	 * @return the hook or a default implementation if none installed.
	 *
	 * @since 5.5
	 */
	public ProtocolV2Hook getProtocolV2Hook() {
		return this.protocolV2Hook != null ? this.protocolV2Hook
				: ProtocolV2Hook.DEFAULT;
	}

	
Set the filter used while advertising the refs to the client.
 Only refs allowed by this filter will be sent to the client. The filter is run against the refs specified by the AdvertiseRefsHook (if applicable). If null or not set, uses the filter implied by the TransferConfig. 
Params:
refFilter – 
           the filter; may be null to show all refs./**
	 * 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 org.eclipse.jgit.transport.AdvertiseRefsHook} (if applicable). If
	 * null or not set, uses the filter implied by the
	 * {@link org.eclipse.jgit.transport.TransferConfig}.
	 *
	 * @param refFilter
	 *            the filter; may be null to show all refs.
	 */
	public void setRefFilter(@Nullable RefFilter refFilter) {
		this.refFilter = refFilter != null ? refFilter : RefFilter.DEFAULT;
	}

	
Get the configured pre upload hook.
Returns:
the configured pre upload hook./**
	 * Get the configured pre upload hook.
	 *
	 * @return the configured pre upload hook.
	 */
	public PreUploadHook getPreUploadHook() {
		return preUploadHook;
	}

	
Set the hook that controls how this instance will behave.
Params:
hook – 
           the hook; if null no special actions are taken./**
	 * Set the hook that controls how this instance will behave.
	 *
	 * @param hook
	 *            the hook; if null no special actions are taken.
	 */
	public void setPreUploadHook(@Nullable PreUploadHook hook) {
		preUploadHook = hook != null ? hook : PreUploadHook.NULL;
	}

	
Get the configured post upload hook.
Returns:
the configured post upload hook.
Since:
4.1/**
	 * Get the configured post upload hook.
	 *
	 * @return the configured post upload hook.
	 * @since 4.1
	 */
	public PostUploadHook getPostUploadHook() {
		return postUploadHook;
	}

	
Set the hook for post upload actions (logging, repacking).
Params:
hook – 
           the hook; if null no special actions are taken.
Since:
4.1/**
	 * Set the hook for post upload actions (logging, repacking).
	 *
	 * @param hook
	 *            the hook; if null no special actions are taken.
	 * @since 4.1
	 */
	public void setPostUploadHook(@Nullable PostUploadHook hook) {
		postUploadHook = hook != null ? hook : PostUploadHook.NULL;
	}

	
Set the configuration used by the pack generator.
Params:
pc – 
           configuration controlling packing parameters. If null the
           source repository's settings will be used./**
	 * 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(@Nullable PackConfig pc) {
		this.packConfig = pc;
	}

	
Set configuration controlling transfer options.
Params:
tc – 
           configuration controlling transfer options. If null the source
           repository's settings will be used.
Since:
3.1/**
	 * Set configuration controlling transfer options.
	 *
	 * @param tc
	 *            configuration controlling transfer options. If null the source
	 *            repository's settings will be used.
	 * @since 3.1
	 */
	public void setTransferConfig(@Nullable TransferConfig tc) {
		this.transferConfig = tc != null ? tc : new TransferConfig(db);
		if (transferConfig.isAllowTipSha1InWant()) {
			setRequestPolicy(transferConfig.isAllowReachableSha1InWant()
				? RequestPolicy.REACHABLE_COMMIT_TIP : RequestPolicy.TIP);
		} else {
			setRequestPolicy(transferConfig.isAllowReachableSha1InWant()
				? RequestPolicy.REACHABLE_COMMIT : RequestPolicy.ADVERTISED);
		}
	}

	
Check whether the client expects a side-band stream.
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.
Returns:
true if the client has advertised a side-band capability, false
    otherwise./**
	 * Check whether the client expects a side-band stream.
	 *
	 * @return true if the client has advertised a side-band capability, false
	 *     otherwise.
	 * @throws org.eclipse.jgit.transport.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 (currentRequest == null) {
			throw new RequestNotYetReadException();
		}
		Set<String> caps = currentRequest.getClientCapabilities();
		return caps.contains(OPTION_SIDE_BAND)
				|| caps.contains(OPTION_SIDE_BAND_64K);
	}

	
Set the Extra Parameters provided by the client.
These are parameters passed by the client through a side channel
such as the Git-Protocol HTTP header, to allow a client to request
a newer response format while remaining compatible with older servers
that do not understand different request formats.
Params:
params – 
           parameters supplied by the client, split at colons or NUL
           bytes.
Since:
5.0/**
	 * Set the Extra Parameters provided by the client.
	 *
	 * <p>These are parameters passed by the client through a side channel
	 * such as the Git-Protocol HTTP header, to allow a client to request
	 * a newer response format while remaining compatible with older servers
	 * that do not understand different request formats.
	 *
	 * @param params
	 *            parameters supplied by the client, split at colons or NUL
	 *            bytes.
	 * @since 5.0
	 */
	public void setExtraParameters(Collection<String> params) {
		this.clientRequestedV2 = params.contains("version=2"); //$NON-NLS-1$
	}

	
Params:
p – provider of URIs corresponding to cached packs (to support
    the packfile URIs feature)
Since:
5.5/**
	 * @param p provider of URIs corresponding to cached packs (to support
	 *     the packfile URIs feature)
	 * @since 5.5
	 */
	public void setCachedPackUriProvider(@Nullable CachedPackUriProvider p) {
		cachedPackUriProvider = p;
	}

	private boolean useProtocolV2() {
		return ProtocolVersion.V2.equals(transferConfig.protocolVersion)
				&& clientRequestedV2;
	}

	
Execute the upload task on the socket.
If the client passed extra parameters (e.g., "version=2") through a
side channel, the caller must call setExtraParameters first to supply
them.
Params:
input – 
           raw input to read client commands from. Caller must ensure the
           input is buffered, otherwise read performance may suffer.
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.
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 – /**
	 * Execute the upload task on the socket.
	 *
	 * <p>If the client passed extra parameters (e.g., "version=2") through a
	 * side channel, the caller must call setExtraParameters first to supply
	 * them.
	 *
	 * @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 java.io.IOException
	 */
	public void upload(InputStream input, OutputStream output,
			@Nullable OutputStream messages) throws IOException {
		PacketLineOut pckOut = null;
		try {
			rawIn = input;
			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);
				@SuppressWarnings("resource")
				TimeoutOutputStream o = new TimeoutOutputStream(output, timer);
				i.setTimeout(timeout * 1000);
				o.setTimeout(timeout * 1000);
				rawIn = i;
				output = o;
			}

			rawOut = new ResponseBufferedOutputStream(output);
			if (biDirectionalPipe) {
				rawOut.stopBuffering();
			}

			pckIn = new PacketLineIn(rawIn);
			pckOut = new PacketLineOut(rawOut);
			if (useProtocolV2()) {
				serviceV2(pckOut);
			} else {
				service(pckOut);
			}
		} catch (UploadPackInternalServerErrorException err) {
			// UploadPackInternalServerErrorException is a special exception
			// that indicates an error is already written to the client. Do
			// nothing.
			throw err;
		} catch (ServiceMayNotContinueException err) {
			if (!err.isOutput() && err.getMessage() != null && pckOut != null) {
				try {
					pckOut.writeString("ERR " + err.getMessage() + "\n"); //$NON-NLS-1$ //$NON-NLS-2$
				} catch (IOException e) {
					err.addSuppressed(e);
					throw err;
				}
				err.setOutput();
			}
			throw err;
		} catch (IOException | RuntimeException | Error err) {
			if (pckOut != null) {
				String msg = err instanceof PackProtocolException
						? err.getMessage()
						: JGitText.get().internalServerError;
				try {
					pckOut.writeString("ERR " + msg + "\n"); //$NON-NLS-1$ //$NON-NLS-2$
				} catch (IOException e) {
					err.addSuppressed(e);
					throw err;
				}
				throw new UploadPackInternalServerErrorException(err);
			}
			throw err;
		} 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.
Returns:
statistics about pack output, if a pack was sent. Null if no pack
        was sent, such as during the negotiation phase of a smart HTTP
        connection, or if the client was already up-to-date.
Since:
4.1/**
	 * 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 negotiation phase of a smart HTTP
	 *         connection, or if the client was already up-to-date.
	 * @since 4.1
	 */
	public PackStatistics getStatistics() {
		return statistics;
	}

	private Map<String, Ref> getAdvertisedOrDefaultRefs() throws IOException {
		if (refs != null) {
			return refs;
		}

		if (!advertiseRefsHookCalled) {
			advertiseRefsHook.advertiseRefs(this);
			advertiseRefsHookCalled = true;
		}
		if (refs == null) {
			// Fall back to all refs.
			setAdvertisedRefs(
					db.getRefDatabase().getRefs().stream()
							.collect(toRefMap((a, b) -> b)));
		}
		return refs;
	}

	private Map<String, Ref> getFilteredRefs(Collection<String> refPrefixes)
					throws IOException {
		if (refPrefixes.isEmpty()) {
			return getAdvertisedOrDefaultRefs();
		}
		if (refs == null && !advertiseRefsHookCalled) {
			advertiseRefsHook.advertiseRefs(this);
			advertiseRefsHookCalled = true;
		}
		if (refs == null) {
			// Fast path: the advertised refs hook did not set advertised refs.
			String[] prefixes = refPrefixes.toArray(new String[0]);
			Map<String, Ref> rs =
					db.getRefDatabase().getRefsByPrefix(prefixes).stream()
							.collect(toRefMap((a, b) -> b));
			if (refFilter != RefFilter.DEFAULT) {
				return refFilter.filter(rs);
			}
			return transferConfig.getRefFilter().filter(rs);
		}

		// Slow path: filter the refs provided by the advertised refs hook.
		// refFilter has already been applied to refs.
		return refs.values().stream()
				.filter(ref -> refPrefixes.stream()
						.anyMatch(ref.getName()::startsWith))
				.collect(toRefMap((a, b) -> b));
	}

	
Returns the specified references.
 This produces an immutable map containing whatever subset of the refs named by the caller are present in the supplied refs map. 
Params:
refs – 
           Map to search for refs to return.
names –  which refs to search for in refs.
Returns:
the requested Refs, omitting any that are null or missing./**
	 * Returns the specified references.
	 * <p>
	 * This produces an immutable map containing whatever subset of the
	 * refs named by the caller are present in the supplied {@code refs}
	 * map.
	 *
	 * @param refs
	 *            Map to search for refs to return.
	 * @param names
	 *            which refs to search for in {@code refs}.
	 * @return the requested Refs, omitting any that are null or missing.
	 */
	@NonNull
	private static Map<String, Ref> mapRefs(
			Map<String, Ref> refs, List<String> names) {
		return unmodifiableMap(
				names.stream()
					.map(refs::get)
					.filter(Objects::nonNull)
						.collect(toRefMap((a, b) -> b)));
	}

	
Read refs on behalf of the client.

This checks whether the refs are present in the ref advertisement
since otherwise the client might not be supposed to be able to
read them.
Params:
names – 
           unabbreviated names of references.
Throws:
IOException – 
           on failure to read a ref or check it for visibility.
Returns:
the requested Refs, omitting any that are not visible or
        do not exist./**
	 * Read refs on behalf of the client.
	 * <p>
	 * This checks whether the refs are present in the ref advertisement
	 * since otherwise the client might not be supposed to be able to
	 * read them.
	 *
	 * @param names
	 *            unabbreviated names of references.
	 * @return the requested Refs, omitting any that are not visible or
	 *         do not exist.
	 * @throws java.io.IOException
	 *            on failure to read a ref or check it for visibility.
	 */
	@NonNull
	private Map<String, Ref> exactRefs(List<String> names) throws IOException {
		if (refs != null) {
			return mapRefs(refs, names);
		}
		if (!advertiseRefsHookCalled) {
			advertiseRefsHook.advertiseRefs(this);
			advertiseRefsHookCalled = true;
		}
		if (refs == null &&
				refFilter == RefFilter.DEFAULT &&
				transferConfig.hasDefaultRefFilter()) {
			// Fast path: no ref filtering is needed.
			String[] ns = names.toArray(new String[0]);
			return unmodifiableMap(db.getRefDatabase().exactRef(ns));
		}
		return mapRefs(getAdvertisedOrDefaultRefs(), names);
	}

	
Find a ref in the usual search path on behalf of the client.

This checks that the ref is present in the ref advertisement since
otherwise the client might not be supposed to be able to read it.
Params:
name – 
           short name of the ref to find, e.g. "master" to find
           "refs/heads/master".
Throws:
IOException – 
           on failure to read the ref or check it for visibility.
Returns:
the requested Ref, or null if it is not visible or does not exist./**
	 * Find a ref in the usual search path on behalf of the client.
	 * <p>
	 * This checks that the ref is present in the ref advertisement since
	 * otherwise the client might not be supposed to be able to read it.
	 *
	 * @param name
	 *            short name of the ref to find, e.g. "master" to find
	 *            "refs/heads/master".
	 * @return the requested Ref, or {@code null} if it is not visible or
	 *         does not exist.
	 * @throws java.io.IOException
	 *            on failure to read the ref or check it for visibility.
	 */
	@Nullable
	private Ref findRef(String name) throws IOException {
		if (refs != null) {
			return RefDatabase.findRef(refs, name);
		}
		if (!advertiseRefsHookCalled) {
			advertiseRefsHook.advertiseRefs(this);
			advertiseRefsHookCalled = true;
		}
		if (refs == null &&
				refFilter == RefFilter.DEFAULT &&
				transferConfig.hasDefaultRefFilter()) {
			// Fast path: no ref filtering is needed.
			return db.getRefDatabase().findRef(name);
		}
		return RefDatabase.findRef(getAdvertisedOrDefaultRefs(), name);
	}

	private void service(PacketLineOut pckOut) throws IOException {
		boolean sendPack = false;
		// If it's a non-bidi request, we need to read the entire request before
		// writing a response. Buffer the response until then.
		PackStatistics.Accumulator accumulator = new PackStatistics.Accumulator();
		List<ObjectId> unshallowCommits = new ArrayList<>();
		FetchRequest req;
		try {
			if (biDirectionalPipe)
				sendAdvertisedRefs(new PacketLineOutRefAdvertiser(pckOut));
			else if (requestValidator instanceof AnyRequestValidator)
				advertised = Collections.emptySet();
			else
				advertised = refIdSet(getAdvertisedOrDefaultRefs().values());

			long negotiateStart = System.currentTimeMillis();
			accumulator.advertised = advertised.size();

			ProtocolV0Parser parser = new ProtocolV0Parser(transferConfig);
			req = parser.recvWants(pckIn);
			currentRequest = req;

			wantIds = req.getWantIds();

			if (req.getWantIds().isEmpty()) {
				preUploadHook.onBeginNegotiateRound(this, req.getWantIds(), 0);
				preUploadHook.onEndNegotiateRound(this, req.getWantIds(), 0, 0,
						false);
				return;
			}
			accumulator.wants = req.getWantIds().size();

			if (req.getClientCapabilities().contains(OPTION_MULTI_ACK_DETAILED)) {
				multiAck = MultiAck.DETAILED;
				noDone = req.getClientCapabilities().contains(OPTION_NO_DONE);
			} else if (req.getClientCapabilities().contains(OPTION_MULTI_ACK))
				multiAck = MultiAck.CONTINUE;
			else
				multiAck = MultiAck.OFF;

			if (!req.getClientShallowCommits().isEmpty()) {
				verifyClientShallow(req.getClientShallowCommits());
			}

			if (req.getDepth() != 0 || req.getDeepenSince() != 0) {
				computeShallowsAndUnshallows(req, shallow -> {
					pckOut.writeString("shallow " + shallow.name() + '\n'); //$NON-NLS-1$
				}, unshallow -> {
					pckOut.writeString("unshallow " + unshallow.name() + '\n'); //$NON-NLS-1$
					unshallowCommits.add(unshallow);
				}, Collections.emptyList());
				pckOut.end();
			}

			if (!req.getClientShallowCommits().isEmpty())
				walk.assumeShallow(req.getClientShallowCommits());
			sendPack = negotiate(req, accumulator, pckOut);
			accumulator.timeNegotiating += System.currentTimeMillis()
					- negotiateStart;

			if (sendPack && !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) {
					sendPack = false;
					throw new CorruptObjectException(MessageFormat.format(
							JGitText.get().expectedEOFReceived,
							"\\x" + Integer.toHexString(eof))); //$NON-NLS-1$
				}
			}
		} finally {
			if (!sendPack && !biDirectionalPipe) {
				while (0 < rawIn.skip(2048) || 0 <= rawIn.read()) {
					// Discard until EOF.
				}
			}
			rawOut.stopBuffering();
		}

		if (sendPack) {
			sendPack(accumulator, req, refs == null ? null : refs.values(),
					unshallowCommits, Collections.emptyList(), pckOut);
		}
	}

	private void lsRefsV2(PacketLineOut pckOut) throws IOException {
		ProtocolV2Parser parser = new ProtocolV2Parser(transferConfig);
		LsRefsV2Request req = parser.parseLsRefsRequest(pckIn);
		protocolV2Hook.onLsRefs(req);

		rawOut.stopBuffering();
		PacketLineOutRefAdvertiser adv = new PacketLineOutRefAdvertiser(pckOut);
		adv.setUseProtocolV2(true);
		if (req.getPeel()) {
			adv.setDerefTags(true);
		}
		Map<String, Ref> refsToSend = getFilteredRefs(req.getRefPrefixes());
		if (req.getSymrefs()) {
			findSymrefs(adv, refsToSend);
		}

		adv.send(refsToSend.values());
		adv.end();
	}

	// Resolves ref names from the request's want-ref lines to
	// object ids, throwing PackProtocolException if any are missing.
	private Map<String, ObjectId> wantedRefs(FetchV2Request req)
			throws IOException {
		Map<String, ObjectId> result = new TreeMap<>();

		List<String> wanted = req.getWantedRefs();
		Map<String, Ref> resolved = exactRefs(wanted);

		for (String refName : wanted) {
			Ref ref = resolved.get(refName);
			if (ref == null) {
				throw new PackProtocolException(MessageFormat
						.format(JGitText.get().invalidRefName, refName));
			}
			ObjectId oid = ref.getObjectId();
			if (oid == null) {
				throw new PackProtocolException(MessageFormat
						.format(JGitText.get().invalidRefName, refName));
			}
			result.put(refName, oid);
		}
		return result;
	}

	private void fetchV2(PacketLineOut pckOut) throws IOException {
		// Depending on the requestValidator, #processHaveLines may
		// require that advertised be set. Set it only in the required
		// circumstances (to avoid a full ref lookup in the case that
		// we don't need it).
		if (requestValidator instanceof TipRequestValidator ||
				requestValidator instanceof ReachableCommitTipRequestValidator ||
				requestValidator instanceof AnyRequestValidator) {
			advertised = Collections.emptySet();
		} else {
			advertised = refIdSet(getAdvertisedOrDefaultRefs().values());
		}

		ProtocolV2Parser parser = new ProtocolV2Parser(transferConfig);
		FetchV2Request req = parser.parseFetchRequest(pckIn);
		currentRequest = req;
		rawOut.stopBuffering();

		protocolV2Hook.onFetch(req);

		if (req.getSidebandAll()) {
			pckOut.setUsingSideband(true);
		}

		// TODO(ifrade): Refactor to pass around the Request object, instead of
		// copying data back to class fields
		List<ObjectId> deepenNots = new ArrayList<>();
		for (String s : req.getDeepenNotRefs()) {
			Ref ref = findRef(s);
			if (ref == null) {
				throw new PackProtocolException(MessageFormat
						.format(JGitText.get().invalidRefName, s));
			}
			deepenNots.add(ref.getObjectId());
		}

		Map<String, ObjectId> wantedRefs = wantedRefs(req);
		// TODO(ifrade): Avoid mutating the parsed request.
		req.getWantIds().addAll(wantedRefs.values());
		wantIds = req.getWantIds();

		boolean sectionSent = false;
		boolean mayHaveShallow = req.getDepth() != 0
				|| req.getDeepenSince() != 0
				|| !req.getDeepenNotRefs().isEmpty();
		List<ObjectId> shallowCommits = new ArrayList<>();
		List<ObjectId> unshallowCommits = new ArrayList<>();

		if (!req.getClientShallowCommits().isEmpty()) {
			verifyClientShallow(req.getClientShallowCommits());
		}
		if (mayHaveShallow) {
			computeShallowsAndUnshallows(req,
					shallowCommit -> shallowCommits.add(shallowCommit),
					unshallowCommit -> unshallowCommits.add(unshallowCommit),
					deepenNots);
		}
		if (!req.getClientShallowCommits().isEmpty())
			walk.assumeShallow(req.getClientShallowCommits());

		if (req.wasDoneReceived()) {
			processHaveLines(req.getPeerHas(), ObjectId.zeroId(),
					new PacketLineOut(NullOutputStream.INSTANCE));
		} else {
			pckOut.writeString("acknowledgments\n"); //$NON-NLS-1$
			for (ObjectId id : req.getPeerHas()) {
				if (walk.getObjectReader().has(id)) {
					pckOut.writeString("ACK " + id.getName() + "\n"); //$NON-NLS-1$ //$NON-NLS-2$
				}
			}
			processHaveLines(req.getPeerHas(), ObjectId.zeroId(),
					new PacketLineOut(NullOutputStream.INSTANCE));
			if (okToGiveUp()) {
				pckOut.writeString("ready\n"); //$NON-NLS-1$
			} else if (commonBase.isEmpty()) {
				pckOut.writeString("NAK\n"); //$NON-NLS-1$
			}
			sectionSent = true;
		}

		if (req.wasDoneReceived() || okToGiveUp()) {
			if (mayHaveShallow) {
				if (sectionSent)
					pckOut.writeDelim();
				pckOut.writeString("shallow-info\n"); //$NON-NLS-1$
				for (ObjectId o : shallowCommits) {
					pckOut.writeString("shallow " + o.getName() + '\n'); //$NON-NLS-1$
				}
				for (ObjectId o : unshallowCommits) {
					pckOut.writeString("unshallow " + o.getName() + '\n'); //$NON-NLS-1$
				}
				sectionSent = true;
			}

			if (!wantedRefs.isEmpty()) {
				if (sectionSent) {
					pckOut.writeDelim();
				}
				pckOut.writeString("wanted-refs\n"); //$NON-NLS-1$
				for (Map.Entry<String, ObjectId> entry :
						wantedRefs.entrySet()) {
					pckOut.writeString(entry.getValue().getName() + ' ' +
							entry.getKey() + '\n');
				}
				sectionSent = true;
			}

			if (sectionSent)
				pckOut.writeDelim();
			if (!pckOut.isUsingSideband()) {
				// sendPack will write "packfile\n" for us if sideband-all is used.
				// But sideband-all is not used, so we have to write it ourselves.
				pckOut.writeString("packfile\n"); //$NON-NLS-1$
			}
			sendPack(new PackStatistics.Accumulator(),
					req,
					req.getClientCapabilities().contains(OPTION_INCLUDE_TAG)
						? db.getRefDatabase().getRefsByPrefix(R_TAGS)
						: null,
					unshallowCommits, deepenNots, pckOut);
			// sendPack invokes pckOut.end() for us, so we do not
			// need to invoke it here.
		} else {
			// Invoke pckOut.end() by ourselves.
			pckOut.end();
		}
	}

	/*
	 * Returns true if this is the last command and we should tear down the
	 * connection.
	 */
	private boolean serveOneCommandV2(PacketLineOut pckOut) throws IOException {
		String command;
		try {
			command = pckIn.readString();
		} catch (EOFException eof) {
			/* EOF when awaiting command is fine */
			return true;
		}
		if (PacketLineIn.isEnd(command)) {
			// A blank request is valid according
			// to the protocol; do nothing in this
			// case.
			return true;
		}
		if (command.equals("command=" + COMMAND_LS_REFS)) { //$NON-NLS-1$
			lsRefsV2(pckOut);
			return false;
		}
		if (command.equals("command=" + COMMAND_FETCH)) { //$NON-NLS-1$
			fetchV2(pckOut);
			return false;
		}
		throw new PackProtocolException(MessageFormat
				.format(JGitText.get().unknownTransportCommand, command));
	}

	@SuppressWarnings("nls")
	private List<String> getV2CapabilityAdvertisement() {
		ArrayList<String> caps = new ArrayList<>();
		caps.add("version 2");
		caps.add(COMMAND_LS_REFS);
		boolean advertiseRefInWant = transferConfig.isAllowRefInWant()
				&& db.getConfig().getBoolean("uploadpack", null,
						"advertiserefinwant", true);
		caps.add(COMMAND_FETCH + '='
				+ (transferConfig.isAllowFilter() ? OPTION_FILTER + ' ' : "")
				+ (advertiseRefInWant ? CAPABILITY_REF_IN_WANT + ' ' : "")
				+ (transferConfig.isAllowSidebandAll()
						? OPTION_SIDEBAND_ALL + ' '
						: "")
				+ (cachedPackUriProvider != null ? "packfile-uris " : "")
				+ OPTION_SHALLOW);
		caps.add(CAPABILITY_SERVER_OPTION);
		return caps;
	}

	private void serviceV2(PacketLineOut pckOut) throws IOException {
		if (biDirectionalPipe) {
			// Just like in service(), the capability advertisement
			// is sent only if this is a bidirectional pipe. (If
			// not, the client is expected to call
			// sendAdvertisedRefs() on its own.)
			protocolV2Hook
					.onCapabilities(CapabilitiesV2Request.builder().build());
			for (String s : getV2CapabilityAdvertisement()) {
				pckOut.writeString(s + "\n"); //$NON-NLS-1$
			}
			pckOut.end();

			while (!serveOneCommandV2(pckOut)) {
				// Repeat until an empty command or EOF.
			}
			return;
		}

		try {
			serveOneCommandV2(pckOut);
		} finally {
			while (0 < rawIn.skip(2048) || 0 <= rawIn.read()) {
				// Discard until EOF.
			}
			rawOut.stopBuffering();
		}
	}

	private static Set<ObjectId> refIdSet(Collection<Ref> refs) {
		Set<ObjectId> ids = new HashSet<>(refs.size());
		for (Ref ref : refs) {
			ObjectId id = ref.getObjectId();
			if (id != null) {
				ids.add(id);
			}
			id = ref.getPeeledObjectId();
			if (id != null) {
				ids.add(id);
			}
		}
		return ids;
	}

	/*
	 * Determines what object ids must be marked as shallow or unshallow for the
	 * client.
	 */
	private void computeShallowsAndUnshallows(FetchRequest req,
			IOConsumer<ObjectId> shallowFunc,
			IOConsumer<ObjectId> unshallowFunc,
			List<ObjectId> deepenNots)
			throws IOException {
		if (req.getClientCapabilities().contains(OPTION_DEEPEN_RELATIVE)) {
			// TODO(jonathantanmy): Implement deepen-relative
			throw new UnsupportedOperationException();
		}

		int walkDepth = req.getDepth() == 0 ? Integer.MAX_VALUE
				: req.getDepth() - 1;
		try (DepthWalk.RevWalk depthWalk = new DepthWalk.RevWalk(
				walk.getObjectReader(), walkDepth)) {

			depthWalk.setDeepenSince(req.getDeepenSince());

			// Find all the commits which will be shallow
			for (ObjectId o : req.getWantIds()) {
				try {
					depthWalk.markRoot(depthWalk.parseCommit(o));
				} catch (IncorrectObjectTypeException notCommit) {
					// Ignore non-commits in this loop.
				}
			}

			depthWalk.setDeepenNots(deepenNots);

			RevCommit o;
			boolean atLeastOne = false;
			while ((o = depthWalk.next()) != null) {
				DepthWalk.Commit c = (DepthWalk.Commit) o;
				atLeastOne = true;

				boolean isBoundary = (c.getDepth() == walkDepth) || c.isBoundary();

				// Commits at the boundary which aren't already shallow in
				// the client need to be marked as such
				if (isBoundary && !req.getClientShallowCommits().contains(c)) {
					shallowFunc.accept(c.copy());
				}

				// Commits not on the boundary which are shallow in the client
				// need to become unshallowed
				if (!isBoundary && req.getClientShallowCommits().remove(c)) {
					unshallowFunc.accept(c.copy());
				}
			}
			if (!atLeastOne) {
				throw new PackProtocolException(
					JGitText.get().noCommitsSelectedForShallow);
			}
		}
	}

	/*
	 * Verify all shallow lines refer to commits
	 *
	 * It can mutate the input set (removing missing object ids from it)
	 */
	private void verifyClientShallow(Set<ObjectId> shallowCommits)
			throws IOException, PackProtocolException {
		AsyncRevObjectQueue q = walk.parseAny(shallowCommits, true);
		try {
			for (;;) {
				try {
					// Shallow objects named by the client must be commits.
					RevObject o = q.next();
					if (o == null) {
						break;
					}
					if (!(o instanceof RevCommit)) {
						throw new PackProtocolException(
							MessageFormat.format(
								JGitText.get().invalidShallowObject,
								o.name()));
					}
				} catch (MissingObjectException notCommit) {
					// shallow objects not known at the server are ignored
					// by git-core upload-pack, match that behavior.
					shallowCommits.remove(notCommit.getObjectId());
					continue;
				}
			}
		} finally {
			q.release();
		}
	}

	
Generate an advertisement of available refs and capabilities.
Params:
adv – 
           the advertisement formatter.
Throws:
IOException – 
           the formatter failed to write an advertisement.
ServiceMayNotContinueException – 
           the hook denied advertisement./**
	 * Generate an advertisement of available refs and capabilities.
	 *
	 * @param adv
	 *            the advertisement formatter.
	 * @throws java.io.IOException
	 *            the formatter failed to write an advertisement.
	 * @throws org.eclipse.jgit.transport.ServiceMayNotContinueException
	 *            the hook denied advertisement.
	 */
	public void sendAdvertisedRefs(RefAdvertiser adv) throws IOException,
			ServiceMayNotContinueException {
		sendAdvertisedRefs(adv, null);
	}

	
Generate an advertisement of available refs and capabilities.
Params:
adv – 
           the advertisement formatter.
serviceName – 
           if not null, also output "# service=serviceName" followed by a
           flush packet before the advertisement. This is required
           in v0 of the HTTP protocol, described in Git's
           Documentation/technical/http-protocol.txt.
Throws:
IOException – 
           the formatter failed to write an advertisement.
ServiceMayNotContinueException – 
           the hook denied advertisement.
Since:
5.0/**
	 * Generate an advertisement of available refs and capabilities.
	 *
	 * @param adv
	 *            the advertisement formatter.
	 * @param serviceName
	 *            if not null, also output "# service=serviceName" followed by a
	 *            flush packet before the advertisement. This is required
	 *            in v0 of the HTTP protocol, described in Git's
	 *            Documentation/technical/http-protocol.txt.
	 * @throws java.io.IOException
	 *            the formatter failed to write an advertisement.
	 * @throws org.eclipse.jgit.transport.ServiceMayNotContinueException
	 *            the hook denied advertisement.
	 * @since 5.0
	 */
	public void sendAdvertisedRefs(RefAdvertiser adv,
			@Nullable String serviceName) throws IOException,
			ServiceMayNotContinueException {
		if (useProtocolV2()) {
			// The equivalent in v2 is only the capabilities
			// advertisement.
			protocolV2Hook
					.onCapabilities(CapabilitiesV2Request.builder().build());
			for (String s : getV2CapabilityAdvertisement()) {
				adv.writeOne(s);
			}
			adv.end();
			return;
		}

		Map<String, Ref> advertisedOrDefaultRefs = getAdvertisedOrDefaultRefs();

		if (serviceName != null) {
			adv.writeOne("# service=" + serviceName + '\n'); //$NON-NLS-1$
			adv.end();
		}
		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);
		if (policy == RequestPolicy.REACHABLE_COMMIT
				|| policy == RequestPolicy.REACHABLE_COMMIT_TIP
				|| policy == null)
			adv.advertiseCapability(OPTION_ALLOW_REACHABLE_SHA1_IN_WANT);
		adv.advertiseCapability(OPTION_AGENT, UserAgent.get());
		if (transferConfig.isAllowFilter()) {
			adv.advertiseCapability(OPTION_FILTER);
		}
		adv.setDerefTags(true);
		findSymrefs(adv, advertisedOrDefaultRefs);
		advertised = adv.send(advertisedOrDefaultRefs.values());

		if (adv.isEmpty())
			adv.advertiseId(ObjectId.zeroId(), "capabilities^{}"); //$NON-NLS-1$
		adv.end();
	}

	
Send a message to the client, if it supports receiving them.

If the client doesn't support receiving messages, the message will be
discarded, with no other indication to the caller or to the client.
Params:
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/**
	 * 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.
		}
	}

	
Get an underlying stream for sending messages to the client
Returns:
an underlying stream for sending messages to the client, or null.
Since:
3.1/**
	 * Get an underlying stream for sending messages to the client
	 *
	 * @return an underlying stream for sending messages to the client, or null.
	 * @since 3.1
	 */
	public OutputStream getMessageOutputStream() {
		return msgOut;
	}

	
Returns the clone/fetch depth. Valid only after calling recvWants(). A
depth of 1 means return only the wants.
Returns:
the depth requested by the client, or 0 if unbounded.
Since:
4.0/**
	 * Returns the clone/fetch depth. Valid only after calling recvWants(). A
	 * depth of 1 means return only the wants.
	 *
	 * @return the depth requested by the client, or 0 if unbounded.
	 * @since 4.0
	 */
	public int getDepth() {
		if (currentRequest == null)
			throw new RequestNotYetReadException();
		return currentRequest.getDepth();
	}

	
Deprecated synonym for getFilterSpec().getBlobLimit(). 
Returns:
filter blob limit requested by the client, or -1 if no limit
Since:
5.3
Deprecated:
Use getFilterSpec() instead/**
	 * Deprecated synonym for {@code getFilterSpec().getBlobLimit()}.
	 *
	 * @return filter blob limit requested by the client, or -1 if no limit
	 * @since 5.3
	 * @deprecated Use {@link #getFilterSpec()} instead
	 */
	@Deprecated
	public final long getFilterBlobLimit() {
		return getFilterSpec().getBlobLimit();
	}

	
Returns the filter spec for the current request. Valid only after
calling recvWants(). This may be a no-op filter spec, but it won't be
null.
Returns:
filter requested by the client
Since:
5.4/**
	 * Returns the filter spec for the current request. Valid only after
	 * calling recvWants(). This may be a no-op filter spec, but it won't be
	 * null.
	 *
	 * @return filter requested by the client
	 * @since 5.4
	 */
	public final FilterSpec getFilterSpec() {
		if (currentRequest == null) {
			throw new RequestNotYetReadException();
		}
		return currentRequest.getFilterSpec();
	}

	
Get the user agent of the client.
 If the client is new enough to use agent= capability that value will be returned. Older HTTP clients may also supply their version using the HTTP User-Agent header. The capability overrides the HTTP header if both are available. 
 When an HTTP request has been received this method returns the HTTP User-Agent header value until capabilities have been parsed. 
Returns:
user agent supplied by the client. Available only if the client
        is new enough to advertise its user agent.
Since:
4.0/**
	 * 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() {
		if (currentRequest != null && currentRequest.getAgent() != null) {
			return currentRequest.getAgent();
		}

		return userAgent;
	}

	private boolean negotiate(FetchRequest req,
			PackStatistics.Accumulator accumulator,
			PacketLineOut pckOut)
			throws IOException {
		okToGiveUp = Boolean.FALSE;

		ObjectId last = ObjectId.zeroId();
		List<ObjectId> peerHas = new ArrayList<>(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 && req.getDepth() > 0)
					return false;
				throw eof;
			}

			if (PacketLineIn.isEnd(line)) {
				last = processHaveLines(peerHas, last, pckOut);
				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)));
				accumulator.haves++;
			} else if (line.equals("done")) { //$NON-NLS-1$
				last = processHaveLines(peerHas, last, pckOut);

				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, PacketLineOut out)
			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)
						out.writeString("ACK " + obj.name() + "\n"); //$NON-NLS-1$ //$NON-NLS-2$
					break;
				case CONTINUE:
					out.writeString("ACK " + obj.name() + " continue\n"); //$NON-NLS-1$ //$NON-NLS-2$
					break;
				case DETAILED:
					out.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:
							out.writeString("ACK " + id.name() + " continue\n"); //$NON-NLS-1$ //$NON-NLS-2$
							break;
						case DETAILED:
							out.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);
			out.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<>();
				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) {
			throw new WantNotValidException(notFound.getObjectId(), notFound);
		} finally {
			q.release();
		}
	}

	private void want(RevObject obj) {
		if (!obj.has(WANT)) {
			obj.add(WANT);
			wantAll.add(obj);
		}
	}

	
Validator corresponding to RequestPolicy.ADVERTISED. 
Since:
3.1/**
	 * Validator corresponding to {@link RequestPolicy#ADVERTISED}.
	 *
	 * @since 3.1
	 */
	public static final class AdvertisedRequestValidator
			implements RequestValidator {
		@Override
		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 WantNotValidException(wants.iterator().next());
		}
	}

	
Validator corresponding to RequestPolicy.REACHABLE_COMMIT. 
Since:
3.1/**
	 * Validator corresponding to {@link RequestPolicy#REACHABLE_COMMIT}.
	 *
	 * @since 3.1
	 */
	public static final class ReachableCommitRequestValidator
			implements RequestValidator {
		@Override
		public void checkWants(UploadPack up, List<ObjectId> wants)
				throws PackProtocolException, IOException {
			checkNotAdvertisedWants(up, wants,
					refIdSet(up.getAdvertisedRefs().values()));
		}
	}

	
Validator corresponding to RequestPolicy.TIP. 
Since:
3.1/**
	 * Validator corresponding to {@link RequestPolicy#TIP}.
	 *
	 * @since 3.1
	 */
	public static final class TipRequestValidator implements RequestValidator {
		@Override
		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());
				for (ObjectId obj : wants) {
					if (!refIds.contains(obj))
						throw new WantNotValidException(obj);
				}
			}
		}
	}

	
Validator corresponding to RequestPolicy.REACHABLE_COMMIT_TIP. 
Since:
3.1/**
	 * Validator corresponding to {@link RequestPolicy#REACHABLE_COMMIT_TIP}.
	 *
	 * @since 3.1
	 */
	public static final class ReachableCommitTipRequestValidator
			implements RequestValidator {
		@Override
		public void checkWants(UploadPack up, List<ObjectId> wants)
				throws PackProtocolException, IOException {
			checkNotAdvertisedWants(up, wants,
					refIdSet(up.getRepository().getRefDatabase().getRefs()));
		}
	}

	
Validator corresponding to RequestPolicy.ANY. 
Since:
3.1/**
	 * Validator corresponding to {@link RequestPolicy#ANY}.
	 *
	 * @since 3.1
	 */
	public static final class AnyRequestValidator implements RequestValidator {
		@Override
		public void checkWants(UploadPack up, List<ObjectId> wants)
				throws PackProtocolException, IOException {
			// All requests are valid.
		}
	}

	private static void checkNotAdvertisedWantsUsingBitmap(ObjectReader reader,
			BitmapIndex bitmapIndex, List<ObjectId> notAdvertisedWants,
			Set<ObjectId> reachableFrom) throws IOException {
		BitmapWalker bitmapWalker = new BitmapWalker(new ObjectWalk(reader), bitmapIndex, null);
		BitmapBuilder reachables = bitmapWalker.findObjects(reachableFrom, null, false);
		for (ObjectId oid : notAdvertisedWants) {
			if (!reachables.contains(oid)) {
				throw new WantNotValidException(oid);
			}
		}
	}

	private static void checkReachabilityByWalkingObjects(ObjectWalk walk,
			List<RevObject> wants, Set<ObjectId> reachableFrom) throws IOException {

		walk.sort(RevSort.TOPO);
		for (RevObject want : wants) {
			walk.markStart(want);
		}
		for (ObjectId have : reachableFrom) {
			RevObject o = walk.parseAny(have);
			walk.markUninteresting(o);

			RevObject peeled = walk.peel(o);
			if (peeled instanceof RevCommit) {
				// By default, for performance reasons, ObjectWalk does not mark a
				// tree as uninteresting when we mark a commit. Mark it ourselves so
				// that we can determine reachability exactly.
				walk.markUninteresting(((RevCommit) peeled).getTree());
			}
		}

		RevCommit commit = walk.next();
		if (commit != null) {
			throw new WantNotValidException(commit);
		}
		RevObject object = walk.nextObject();
		if (object != null) {
			throw new WantNotValidException(object);
		}
	}

	private static void checkNotAdvertisedWants(UploadPack up,
			List<ObjectId> notAdvertisedWants, Set<ObjectId> reachableFrom)
			throws IOException {

		ObjectReader reader = up.getRevWalk().getObjectReader();
		try (RevWalk walk = new RevWalk(reader)) {
			walk.setRetainBody(false);
			// Missing "wants" throw exception here
			List<RevObject> wantsAsObjs = objectIdsToRevObjects(walk,
					notAdvertisedWants);
			List<RevCommit> wantsAsCommits = wantsAsObjs.stream()
					.filter(obj -> obj instanceof RevCommit)
					.map(obj -> (RevCommit) obj)
					.collect(Collectors.toList());
			boolean allWantsAreCommits = wantsAsObjs.size() == wantsAsCommits
					.size();
			boolean repoHasBitmaps = reader.getBitmapIndex() != null;

			if (!allWantsAreCommits) {
				if (!repoHasBitmaps) {
					if (up.transferConfig.isAllowFilter()) {
						// Use allowFilter as an indication that the server
						// operator is willing to pay the cost of these
						// reachability checks.
						try (ObjectWalk objWalk = walk.toObjectWalkWithSameObjects()) {
							checkReachabilityByWalkingObjects(objWalk,
									wantsAsObjs, reachableFrom);
						}
						return;
					}

					// If unadvertized non-commits are requested, use
					// bitmaps. If there are no bitmaps, instead of
					// incurring the expense of a manual walk, reject
					// the request.
					RevObject nonCommit = wantsAsObjs
							.stream()
							.filter(obj -> !(obj instanceof RevCommit))
							.limit(1)
							.collect(Collectors.toList()).get(0);
					throw new WantNotValidException(nonCommit);

				}
				checkNotAdvertisedWantsUsingBitmap(reader,
						reader.getBitmapIndex(), notAdvertisedWants,
						reachableFrom);
				return;
			}

			// All wants are commits, we can use ReachabilityChecker
			ReachabilityChecker reachabilityChecker = walk
					.createReachabilityChecker();

			List<RevCommit> starters = objectIdsToRevCommits(walk,
					reachableFrom);
			Optional<RevCommit> unreachable = reachabilityChecker
					.areAllReachable(wantsAsCommits, starters);
			if (unreachable.isPresent()) {
				throw new WantNotValidException(unreachable.get());
			}

		} catch (MissingObjectException notFound) {
			throw new WantNotValidException(notFound.getObjectId(), notFound);
		}
	}

	// Resolve the ObjectIds into RevObjects. Any missing object raises an
	// exception
	private static List<RevObject> objectIdsToRevObjects(RevWalk walk,
			Iterable<ObjectId> objectIds)
			throws MissingObjectException, IOException {
		List<RevObject> result = new ArrayList<>();
		for (ObjectId objectId : objectIds) {
			result.add(walk.parseAny(objectId));
		}
		return result;
	}

	// Get commits from object ids. If the id is not a commit, ignore it. If the
	// id doesn't exist, report the missing object in a exception.
	private static List<RevCommit> objectIdsToRevCommits(RevWalk walk,
			Iterable<ObjectId> objectIds)
			throws MissingObjectException, IOException {
		List<RevCommit> result = new ArrayList<>();
		for (ObjectId objectId : objectIds) {
			try {
				result.add(walk.parseCommit(objectId));
			} catch (IncorrectObjectTypeException e) {
				continue;
			}
		}
		return result;
	}


	private void addCommonBase(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(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;
	}

	
Send the requested objects to the client.
Params:
accumulator – 
           where to write statistics about the content of the pack.
req – 
           request in process
allTags –  refs to search for annotated tags to include in the pack if the GitProtocolConstants.OPTION_INCLUDE_TAG capability was requested.
unshallowCommits – 
           shallow commits on the client that are now becoming unshallow
deepenNots – 
           objects that the client specified using --shallow-exclude
pckOut – 
           output writer
Throws:
IOException – 
            if an error occurred while generating or writing the pack./**
	 * Send the requested objects to the client.
	 *
	 * @param accumulator
	 *            where to write statistics about the content of the pack.
	 * @param req
	 *            request in process
	 * @param allTags
	 *            refs to search for annotated tags to include in the pack if
	 *            the {@link #OPTION_INCLUDE_TAG} capability was requested.
	 * @param unshallowCommits
	 *            shallow commits on the client that are now becoming unshallow
	 * @param deepenNots
	 *            objects that the client specified using --shallow-exclude
	 * @param pckOut
	 *            output writer
	 * @throws IOException
	 *             if an error occurred while generating or writing the pack.
	 */
	private void sendPack(PackStatistics.Accumulator accumulator,
			FetchRequest req,
			@Nullable Collection<Ref> allTags,
			List<ObjectId> unshallowCommits,
			List<ObjectId> deepenNots,
			PacketLineOut pckOut) throws IOException {
		Set<String> caps = req.getClientCapabilities();
		boolean sideband = caps.contains(OPTION_SIDE_BAND)
				|| caps.contains(OPTION_SIDE_BAND_64K);
		if (sideband) {
			try {
				sendPack(true, req, accumulator, allTags, unshallowCommits,
						deepenNots, pckOut);
			} catch (ServiceMayNotContinueException err) {
				String message = err.getMessage();
				if (message == null) {
					message = JGitText.get().internalServerError;
				}
				try {
					reportInternalServerErrorOverSideband(message);
				} catch (IOException e) {
					err.addSuppressed(e);
					throw err;
				}
				throw new UploadPackInternalServerErrorException(err);
			} catch (IOException | RuntimeException | Error err) {
				try {
					reportInternalServerErrorOverSideband(
							JGitText.get().internalServerError);
				} catch (IOException e) {
					err.addSuppressed(e);
					throw err;
				}
				throw new UploadPackInternalServerErrorException(err);
			}
		} else {
			sendPack(false, req, accumulator, allTags, unshallowCommits, deepenNots,
					pckOut);
		}
	}

	private void reportInternalServerErrorOverSideband(String message)
			throws IOException {
		@SuppressWarnings("resource" /* java 7 */)
		SideBandOutputStream err = new SideBandOutputStream(
				SideBandOutputStream.CH_ERROR, SideBandOutputStream.SMALL_BUF,
				rawOut);
		err.write(Constants.encode(message));
		err.flush();
	}

	
Send the requested objects to the client.
Params:
sideband – 
           whether to wrap the pack in side-band pkt-lines, interleaved
           with progress messages and errors.
req – 
           request being processed
accumulator – 
           where to write statistics about the content of the pack.
allTags –  refs to search for annotated tags to include in the pack if the GitProtocolConstants.OPTION_INCLUDE_TAG capability was requested.
unshallowCommits – 
           shallow commits on the client that are now becoming unshallow
deepenNots – 
           objects that the client specified using --shallow-exclude
pckOut – 
           output writer
Throws:
IOException – 
            if an error occurred while generating or writing the pack./**
	 * Send the requested objects to the client.
	 *
	 * @param sideband
	 *            whether to wrap the pack in side-band pkt-lines, interleaved
	 *            with progress messages and errors.
	 * @param req
	 *            request being processed
	 * @param accumulator
	 *            where to write statistics about the content of the pack.
	 * @param allTags
	 *            refs to search for annotated tags to include in the pack if
	 *            the {@link #OPTION_INCLUDE_TAG} capability was requested.
	 * @param unshallowCommits
	 *            shallow commits on the client that are now becoming unshallow
	 * @param deepenNots
	 *            objects that the client specified using --shallow-exclude
	 * @param pckOut
	 *            output writer
	 * @throws IOException
	 *             if an error occurred while generating or writing the pack.
	 */
	private void sendPack(final boolean sideband,
			FetchRequest req,
			PackStatistics.Accumulator accumulator,
			@Nullable Collection<Ref> allTags,
			List<ObjectId> unshallowCommits,
			List<ObjectId> deepenNots,
			PacketLineOut pckOut) throws IOException {
		ProgressMonitor pm = NullProgressMonitor.INSTANCE;
		OutputStream packOut = rawOut;

		if (sideband) {
			int bufsz = SideBandOutputStream.SMALL_BUF;
			if (req.getClientCapabilities().contains(OPTION_SIDE_BAND_64K))
				bufsz = SideBandOutputStream.MAX_BUF;

			packOut = new SideBandOutputStream(SideBandOutputStream.CH_DATA,
					bufsz, rawOut);
			if (!req.getClientCapabilities().contains(OPTION_NO_PROGRESS)) {
				msgOut = new SideBandOutputStream(
						SideBandOutputStream.CH_PROGRESS, bufsz, rawOut);
				pm = new SideBandProgressMonitor(msgOut);
			}
		}

		if (wantAll.isEmpty()) {
			preUploadHook.onSendPack(this, wantIds, commonBase);
		} else {
			preUploadHook.onSendPack(this, wantAll, commonBase);
		}
		msgOut.flush();

		PackConfig cfg = packConfig;
		if (cfg == null)
			cfg = new PackConfig(db);
		@SuppressWarnings("resource") // PackWriter is referenced in the finally
										// block, and is closed there
		final PackWriter pw = new PackWriter(cfg, walk.getObjectReader(),
				accumulator);
		try {
			pw.setIndexDisabled(true);
			if (req.getFilterSpec().isNoOp()) {
				pw.setUseCachedPacks(true);
			} else {
				pw.setFilterSpec(req.getFilterSpec());
				pw.setUseCachedPacks(false);
			}
			pw.setUseBitmaps(
					req.getDepth() == 0
							&& req.getClientShallowCommits().isEmpty()
							&& req.getFilterSpec().getTreeDepthLimit() == -1);
			pw.setClientShallowCommits(req.getClientShallowCommits());
			pw.setReuseDeltaCommits(true);
			pw.setDeltaBaseAsOffset(
					req.getClientCapabilities().contains(OPTION_OFS_DELTA));
			pw.setThin(req.getClientCapabilities().contains(OPTION_THIN_PACK));
			pw.setReuseValidatingObjects(false);

			// Objects named directly by references go at the beginning
			// of the pack.
			if (commonBase.isEmpty() && refs != null) {
				Set<ObjectId> tagTargets = new HashSet<>();
				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);
			}

			RevWalk rw = walk;
			if (req.getDepth() > 0 || req.getDeepenSince() != 0 || !deepenNots.isEmpty()) {
				int walkDepth = req.getDepth() == 0 ? Integer.MAX_VALUE
						: req.getDepth() - 1;
				pw.setShallowPack(req.getDepth(), unshallowCommits);

				@SuppressWarnings("resource") // Ownership is transferred below
				DepthWalk.RevWalk dw = new DepthWalk.RevWalk(
						walk.getObjectReader(), walkDepth);
				dw.setDeepenSince(req.getDeepenSince());
				dw.setDeepenNots(deepenNots);
				dw.assumeShallow(req.getClientShallowCommits());
				rw = dw;
			}

			if (wantAll.isEmpty()) {
				pw.preparePack(pm, wantIds, commonBase,
						req.getClientShallowCommits());
			} else {
				walk.reset();

				ObjectWalk ow = rw.toObjectWalkWithSameObjects();
				pw.preparePack(pm, ow, wantAll, commonBase, PackWriter.NONE);
				rw = ow;
			}

			if (req.getClientCapabilities().contains(OPTION_INCLUDE_TAG)
					&& allTags != null) {
				for (Ref ref : allTags) {
					ObjectId objectId = ref.getObjectId();
					if (objectId == null) {
						// skip unborn branch
						continue;
					}

					// 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.getRefDatabase().peel(ref);

					ObjectId peeledId = ref.getPeeledObjectId();
					objectId = ref.getObjectId();
					if (peeledId == null || objectId == null)
						continue;

					objectId = ref.getObjectId();
					if (pw.willInclude(peeledId) && !pw.willInclude(objectId)) {
						RevObject o = rw.parseAny(objectId);
						addTagChain(o, pw);
						pw.addObject(o);
					}
				}
			}

			if (pckOut.isUsingSideband()) {
				if (req instanceof FetchV2Request &&
						cachedPackUriProvider != null &&
						!((FetchV2Request) req).getPackfileUriProtocols().isEmpty()) {
					FetchV2Request reqV2 = (FetchV2Request) req;
					pw.setPackfileUriConfig(new PackWriter.PackfileUriConfig(
							pckOut,
							reqV2.getPackfileUriProtocols(),
							cachedPackUriProvider));
				} else {
					// PackWriter will write "packfile-uris\n" and "packfile\n"
					// for us if provided a PackfileUriConfig. In this case, we
					// are not providing a PackfileUriConfig, so we have to
					// write this line ourselves.
					pckOut.writeString("packfile\n"); //$NON-NLS-1$
				}
			}
			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) {
				postUploadHook.onPostUpload(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());
		}
	}

	private void addTagChain(
			RevObject o, PackWriter pw) throws IOException {
		while (Constants.OBJ_TAG == o.getType()) {
			RevTag t = (RevTag) o;
			o = t.getObject();
			if (o.getType() == Constants.OBJ_TAG && !pw.willInclude(o.getId())) {
				walk.parseBody(o);
				pw.addObject(o);
			}
		}
	}

	private static class ResponseBufferedOutputStream extends OutputStream {
		private final OutputStream rawOut;

		private OutputStream out;

		ResponseBufferedOutputStream(OutputStream rawOut) {
			this.rawOut = rawOut;
			this.out = new ByteArrayOutputStream();
		}

		@Override
		public void write(int b) throws IOException {
			out.write(b);
		}

		@Override
		public void write(byte b[]) throws IOException {
			out.write(b);
		}

		@Override
		public void write(byte b[], int off, int len) throws IOException {
			out.write(b, off, len);
		}

		@Override
		public void flush() throws IOException {
			out.flush();
		}

		@Override
		public void close() throws IOException {
			out.close();
		}

		void stopBuffering() throws IOException {
			if (out != rawOut) {
				((ByteArrayOutputStream) out).writeTo(rawOut);
				out = rawOut;
			}
		}
	}
}