/*
    * 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.nio.charset.StandardCharsets.UTF_8;
  import static org.eclipse.jgit.transport.GitProtocolConstants.CAPABILITY_ATOMIC;
  import static org.eclipse.jgit.transport.GitProtocolConstants.CAPABILITY_DELETE_REFS;
  import static org.eclipse.jgit.transport.GitProtocolConstants.CAPABILITY_OFS_DELTA;
  import static org.eclipse.jgit.transport.GitProtocolConstants.CAPABILITY_PUSH_OPTIONS;
  import static org.eclipse.jgit.transport.GitProtocolConstants.CAPABILITY_QUIET;
  import static org.eclipse.jgit.transport.GitProtocolConstants.CAPABILITY_REPORT_STATUS;
  import static org.eclipse.jgit.transport.GitProtocolConstants.CAPABILITY_SIDE_BAND_64K;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_AGENT;
  import static org.eclipse.jgit.transport.SideBandOutputStream.CH_DATA;
  import static org.eclipse.jgit.transport.SideBandOutputStream.CH_ERROR;
  import static org.eclipse.jgit.transport.SideBandOutputStream.CH_PROGRESS;
  import static org.eclipse.jgit.transport.SideBandOutputStream.MAX_BUF;
  
  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.Collections;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.concurrent.TimeUnit;
  
  import org.eclipse.jgit.annotations.Nullable;
  import org.eclipse.jgit.errors.InvalidObjectIdException;
  import org.eclipse.jgit.errors.LargeObjectException;
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.errors.PackProtocolException;
  import org.eclipse.jgit.errors.TooLargePackException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.internal.storage.file.PackLock;
  import org.eclipse.jgit.internal.submodule.SubmoduleValidator;
  import org.eclipse.jgit.internal.submodule.SubmoduleValidator.SubmoduleValidationException;
  import org.eclipse.jgit.internal.transport.parser.FirstCommand;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.BatchRefUpdate;
  import org.eclipse.jgit.lib.Config;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.GitmoduleEntry;
  import org.eclipse.jgit.lib.NullProgressMonitor;
  import org.eclipse.jgit.lib.ObjectChecker;
  import org.eclipse.jgit.lib.ObjectDatabase;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectIdSubclassMap;
  import org.eclipse.jgit.lib.ObjectInserter;
  import org.eclipse.jgit.lib.ObjectLoader;
  import org.eclipse.jgit.lib.PersonIdent;
  import org.eclipse.jgit.lib.ProgressMonitor;
  import org.eclipse.jgit.lib.Ref;
  import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.ObjectWalk;
 import org.eclipse.jgit.revwalk.RevBlob;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevFlag;
 import org.eclipse.jgit.revwalk.RevObject;
 import org.eclipse.jgit.revwalk.RevSort;
 import org.eclipse.jgit.revwalk.RevTree;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.transport.PacketLineIn.InputOverLimitIOException;
 import org.eclipse.jgit.transport.ReceiveCommand.Result;
 import org.eclipse.jgit.util.io.InterruptTimer;
 import org.eclipse.jgit.util.io.LimitedInputStream;
 import org.eclipse.jgit.util.io.TimeoutInputStream;
 import org.eclipse.jgit.util.io.TimeoutOutputStream;
 
 /**
  * Base implementation of the side of a push connection that receives objects.
  * <p>
  * Contains high-level operations for initializing and closing streams,
  * advertising refs, reading commands, and receiving and applying a pack.
  * Subclasses compose these operations into full service implementations.
  */
 public abstract class BaseReceivePack {
 	/**
 	 * Data in the first line of a request, the line itself plus capabilities.
 	 *
 	 * @deprecated Use {@link FirstCommand} instead.
 	 */
 	@Deprecated
 	public static class FirstLine {
 		private final FirstCommand command;
 
 		/**
 		 * Parse the first line of a receive-pack request.
 		 *
 		 * @param line
 		 *            line from the client.
 		 */
 		public FirstLine(String line) {
 			command = FirstCommand.fromLine(line);
 		}
 
 		/** @return non-capabilities part of the line. */
 		public String getLine() {
 			return command.getLine();
 		}
 
 		/** @return capabilities parsed from the line. */
 		public Set<String> getCapabilities() {
 			return command.getCapabilities();
 		}
 	}
 
 	/** Database we write the stored objects into. */
 	final Repository db;
 
 	/** Revision traversal support over {@link #db}. */
 	final RevWalk walk;
 
 	/**
 	 * 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;
 
 	/** Expecting data after the pack footer */
 	private boolean expectDataAfterPackFooter;
 
 	/** Should an incoming transfer validate objects? */
 	private ObjectChecker objectChecker;
 
 	/** Should an incoming transfer permit create requests? */
 	private boolean allowCreates;
 
 	/** Should an incoming transfer permit delete requests? */
 	private boolean allowAnyDeletes;
 	private boolean allowBranchDeletes;
 
 	/** Should an incoming transfer permit non-fast-forward requests? */
 	private boolean allowNonFastForwards;
 
 	/** Should an incoming transfer permit push options? **/
 	private boolean allowPushOptions;
 
 	/**
 	 * Should the requested ref updates be performed as a single atomic
 	 * transaction?
 	 */
 	private boolean atomic;
 
 	private boolean allowOfsDelta;
 	private boolean allowQuiet = true;
 
 	/** Identity to record action as within the reflog. */
 	private PersonIdent refLogIdent;
 
 	/** Hook used while advertising the refs to the client. */
 	private AdvertiseRefsHook advertiseRefsHook;
 
 	/** Filter used while advertising the refs to the client. */
 	RefFilter refFilter;
 
 	/** Timeout in seconds to wait for client interaction. */
 	private int timeout;
 
 	/** Timer to manage {@link #timeout}. */
 	private InterruptTimer timer;
 
 	private TimeoutInputStream timeoutIn;
 
 	// Original stream passed to init(), since rawOut may be wrapped in a
 	// sideband.
 	private OutputStream origOut;
 
 	/** Raw input stream. */
 	protected InputStream rawIn;
 
 	/** Raw output stream. */
 	protected OutputStream rawOut;
 
 	/** Optional message output stream. */
 	protected OutputStream msgOut;
 	private SideBandOutputStream errOut;
 
 	/** Packet line input stream around {@link #rawIn}. */
 	protected PacketLineIn pckIn;
 
 	/** Packet line output stream around {@link #rawOut}. */
 	protected PacketLineOut pckOut;
 
 	private final MessageOutputWrapper msgOutWrapper = new MessageOutputWrapper();
 
 	private PackParser parser;
 
 	/** The refs we advertised as existing at the start of the connection. */
 	Map<String, Ref> refs;
 
 	/** All SHA-1s shown to the client, which can be possible edges. */
 	Set<ObjectId> advertisedHaves;
 
 	/** Capabilities requested by the client. */
 	private Set<String> enabledCapabilities;
 	String userAgent;
 	private Set<ObjectId> clientShallowCommits;
 	private List<ReceiveCommand> commands;
 	private long maxCommandBytes;
 	private long maxDiscardBytes;
 
 	private StringBuilder advertiseError;
 
 	/** If {@link BasePackPushConnection#CAPABILITY_SIDE_BAND_64K} is enabled. */
 	private boolean sideBand;
 
 	private boolean quiet;
 
 	/** Lock around the received pack file, while updating refs. */
 	private PackLock packLock;
 
 	private boolean checkReferencedIsReachable;
 
 	/** Git object size limit */
 	private long maxObjectSizeLimit;
 
 	/** Total pack size limit */
 	private long maxPackSizeLimit = -1;
 
 	/** The size of the received pack, including index size */
 	private Long packSize;
 
 	private PushCertificateParser pushCertificateParser;
 	private SignedPushConfig signedPushConfig;
 	PushCertificate pushCert;
 	private ReceivedPackStatistics stats;
 
 	/**
 	 * Get the push certificate used to verify the pusher's identity.
 	 * <p>
 	 * Only valid after commands are read from the wire.
 	 *
 	 * @return the parsed certificate, or null if push certificates are disabled
 	 *         or no cert was presented by the client.
 	 * @since 4.1
 	 * @deprecated use {@link ReceivePack#getPushCertificate}.
 	 */
 	@Deprecated
 	public abstract PushCertificate getPushCertificate();
 
 	/**
 	 * Set the push certificate used to verify the pusher's identity.
 	 * <p>
 	 * Should only be called if reconstructing an instance without going through
 	 * the normal {@link #recvCommands()} flow.
 	 *
 	 * @param cert
 	 *            the push certificate to set.
 	 * @since 4.1
 	 * @deprecated use {@link ReceivePack#setPushCertificate(PushCertificate)}.
 	 */
 	@Deprecated
 	public abstract void setPushCertificate(PushCertificate cert);
 
 	/**
 	 * Create a new pack receive for an open repository.
 	 *
 	 * @param into
 	 *            the destination repository.
 	 */
 	protected BaseReceivePack(Repository into) {
 		db = into;
 		walk = new RevWalk(db);
 		walk.setRetainBody(false);
 
 		TransferConfig tc = db.getConfig().get(TransferConfig.KEY);
 		objectChecker = tc.newReceiveObjectChecker();
 
 		ReceiveConfig rc = db.getConfig().get(ReceiveConfig::new);
 		allowCreates = rc.allowCreates;
 		allowAnyDeletes = true;
 		allowBranchDeletes = rc.allowDeletes;
 		allowNonFastForwards = rc.allowNonFastForwards;
 		allowOfsDelta = rc.allowOfsDelta;
 		allowPushOptions = rc.allowPushOptions;
 		maxCommandBytes = rc.maxCommandBytes;
 		maxDiscardBytes = rc.maxDiscardBytes;
 		advertiseRefsHook = AdvertiseRefsHook.DEFAULT;
 		refFilter = RefFilter.DEFAULT;
 		advertisedHaves = new HashSet<>();
 		clientShallowCommits = new HashSet<>();
 		signedPushConfig = rc.signedPush;
 	}
 
 	/** Configuration for receive operations. */
 	protected static class ReceiveConfig {
 		final boolean allowCreates;
 		final boolean allowDeletes;
 		final boolean allowNonFastForwards;
 		final boolean allowOfsDelta;
 		final boolean allowPushOptions;
 		final long maxCommandBytes;
 		final long maxDiscardBytes;
 		final SignedPushConfig signedPush;
 
 		ReceiveConfig(Config config) {
 			allowCreates = true;
 			allowDeletes = !config.getBoolean("receive", "denydeletes", false); //$NON-NLS-1$ //$NON-NLS-2$
 			allowNonFastForwards = !config.getBoolean("receive", //$NON-NLS-1$
 					"denynonfastforwards", false); //$NON-NLS-1$
 			allowOfsDelta = config.getBoolean("repack", "usedeltabaseoffset", //$NON-NLS-1$ //$NON-NLS-2$
 					true);
 			allowPushOptions = config.getBoolean("receive", "pushoptions", //$NON-NLS-1$ //$NON-NLS-2$
 					false);
 			maxCommandBytes = config.getLong("receive", //$NON-NLS-1$
 					"maxCommandBytes", //$NON-NLS-1$
 					3 << 20);
 			maxDiscardBytes = config.getLong("receive", //$NON-NLS-1$
 					"maxCommandDiscardBytes", //$NON-NLS-1$
 					-1);
 			signedPush = SignedPushConfig.KEY.parse(config);
 		}
 	}
 
 	/**
 	 * Output stream that wraps the current {@link #msgOut}.
 	 * <p>
 	 * We don't want to expose {@link #msgOut} directly because it can change
 	 * several times over the course of a session.
 	 */
 	class MessageOutputWrapper extends OutputStream {
 		@Override
 		public void write(int ch) {
 			if (msgOut != null) {
 				try {
 					msgOut.write(ch);
 				} catch (IOException e) {
 					// Ignore write failures.
 				}
 			}
 		}
 
 		@Override
 		public void write(byte[] b, int off, int len) {
 			if (msgOut != null) {
 				try {
 					msgOut.write(b, off, len);
 				} catch (IOException e) {
 					// Ignore write failures.
 				}
 			}
 		}
 
 		@Override
 		public void write(byte[] b) {
 			write(b, 0, b.length);
 		}
 
 		@Override
 		public void flush() {
 			if (msgOut != null) {
 				try {
 					msgOut.flush();
 				} catch (IOException e) {
 					// Ignore write failures.
 				}
 			}
 		}
 	}
 
 	/**
 	 * Get the process name used for pack lock messages.
 	 *
 	 * @return the process name used for pack lock messages.
 	 */
 	protected abstract String getLockMessageProcessName();
 
 	/**
 	 * Get the repository this receive completes into.
 	 *
 	 * @return the repository this receive completes into.
 	 * @deprecated use {@link ReceivePack#getRepository}
 	 */
 	@Deprecated
 	public abstract Repository getRepository();
 
 	/**
 	 * Get the RevWalk instance used by this connection.
 	 *
 	 * @return the RevWalk instance used by this connection.
 	 * @deprecated use {@link ReceivePack#getRevWalk}
 	 */
 	@Deprecated
 	public abstract RevWalk getRevWalk();
 
 	/**
 	 * Get refs which were advertised to the client.
 	 *
 	 * @return all refs which were advertised to the client, or null if
 	 *         {@link #setAdvertisedRefs(Map, Set)} has not been called yet.
 	 * @deprecated use {@link ReceivePack#getAdvertisedRefs}
 	 */
 	@Deprecated
 	public abstract Map<String, Ref> getAdvertisedRefs();
 
 	/**
 	 * Set the refs advertised by this ReceivePack.
 	 * <p>
 	 * Intended to be called from a
 	 * {@link org.eclipse.jgit.transport.PreReceiveHook}.
 	 *
 	 * @param allRefs
 	 *            explicit set of references to claim as advertised by this
 	 *            ReceivePack 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.
 	 * @param additionalHaves
 	 *            explicit set of additional haves to claim as advertised. If
 	 *            null, assumes the default set of additional haves from the
 	 *            repository.
 	 * @deprecated use {@link ReceivePack#setAdvertisedRefs}
 	 */
 	@Deprecated
 	public abstract void setAdvertisedRefs(Map<String, Ref> allRefs, Set<ObjectId> additionalHaves);
 
 	/**
 	 * Get objects advertised to the client.
 	 *
 	 * @return the set of objects advertised to the as present in this repository,
 	 *         or null if {@link #setAdvertisedRefs(Map, Set)} has not been called
 	 *         yet.
 	 */
 	public final Set<ObjectId> getAdvertisedObjects() {
 		return advertisedHaves;
 	}
 
 	/**
 	 * Whether this instance will validate all referenced, but not supplied by
 	 * the client, objects are reachable from another reference.
 	 *
 	 * @return true if this instance will validate all referenced, but not
 	 *         supplied by the client, objects are reachable from another
 	 *         reference.
 	 */
 	public boolean isCheckReferencedObjectsAreReachable() {
 		return checkReferencedIsReachable;
 	}
 
 	/**
 	 * Validate all referenced but not supplied objects are reachable.
 	 * <p>
 	 * If enabled, this instance will verify that references to objects not
 	 * contained within the received pack are already reachable through at least
 	 * one other reference displayed as part of {@link #getAdvertisedRefs()}.
 	 * <p>
 	 * This feature is useful when the application doesn't trust the client to
 	 * not provide a forged SHA-1 reference to an object, in an attempt to
 	 * access parts of the DAG that they aren't allowed to see and which have
 	 * been hidden from them via the configured
 	 * {@link org.eclipse.jgit.transport.AdvertiseRefsHook} or
 	 * {@link org.eclipse.jgit.transport.RefFilter}.
 	 * <p>
 	 * Enabling this feature may imply at least some, if not all, of the same
 	 * functionality performed by {@link #setCheckReceivedObjects(boolean)}.
 	 * Applications are encouraged to enable both features, if desired.
 	 *
 	 * @param b
 	 *            {@code true} to enable the additional check.
 	 */
 	public void setCheckReferencedObjectsAreReachable(boolean b) {
 		this.checkReferencedIsReachable = b;
 	}
 
 	/**
 	 * 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;
 	}
 
 	/**
 	 * Whether 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.
 	 *
 	 * @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;
 	}
 
 	/**
 	 * Whether there is data expected after the pack footer.
 	 *
 	 * @return {@code true} if there is data expected after the pack footer.
 	 */
 	public boolean isExpectDataAfterPackFooter() {
 		return expectDataAfterPackFooter;
 	}
 
 	/**
 	 * Whether there is additional data in InputStream after pack.
 	 *
 	 * @param e
 	 *            {@code true} if there is additional data in InputStream after
 	 *            pack.
 	 */
 	public void setExpectDataAfterPackFooter(boolean e) {
 		expectDataAfterPackFooter = e;
 	}
 
 	/**
 	 * Whether this instance will verify received objects are formatted
 	 * correctly.
 	 *
 	 * @return {@code true} if this instance will verify received objects are
 	 *         formatted correctly. Validating objects requires more CPU time on
 	 *         this side of the connection.
 	 */
 	public boolean isCheckReceivedObjects() {
 		return objectChecker != null;
 	}
 
 	/**
 	 * Whether to enable checking received objects
 	 *
 	 * @param check
 	 *            {@code true} to enable checking received objects; false to
 	 *            assume all received objects are valid.
 	 * @see #setObjectChecker(ObjectChecker)
 	 */
 	public void setCheckReceivedObjects(boolean check) {
 		if (check && objectChecker == null)
 			setObjectChecker(new ObjectChecker());
 		else if (!check && objectChecker != null)
 			setObjectChecker(null);
 	}
 
 	/**
 	 * Set the object checking instance to verify each received object with
 	 *
 	 * @param impl
 	 *            if non-null the object checking instance to verify each
 	 *            received object with; null to disable object checking.
 	 * @since 3.4
 	 */
 	public void setObjectChecker(ObjectChecker impl) {
 		objectChecker = impl;
 	}
 
 	/**
 	 * Whether the client can request refs to be created.
 	 *
 	 * @return {@code true} if the client can request refs to be created.
 	 */
 	public boolean isAllowCreates() {
 		return allowCreates;
 	}
 
 	/**
 	 * Whether to permit create ref commands to be processed.
 	 *
 	 * @param canCreate
 	 *            {@code true} to permit create ref commands to be processed.
 	 */
 	public void setAllowCreates(boolean canCreate) {
 		allowCreates = canCreate;
 	}
 
 	/**
 	 * Whether the client can request refs to be deleted.
 	 *
 	 * @return {@code true} if the client can request refs to be deleted.
 	 */
 	public boolean isAllowDeletes() {
 		return allowAnyDeletes;
 	}
 
 	/**
 	 * Whether to permit delete ref commands to be processed.
 	 *
 	 * @param canDelete
 	 *            {@code true} to permit delete ref commands to be processed.
 	 */
 	public void setAllowDeletes(boolean canDelete) {
 		allowAnyDeletes = canDelete;
 	}
 
 	/**
 	 * Whether the client can delete from {@code refs/heads/}.
 	 *
 	 * @return {@code true} if the client can delete from {@code refs/heads/}.
 	 * @since 3.6
 	 */
 	public boolean isAllowBranchDeletes() {
 		return allowBranchDeletes;
 	}
 
 	/**
 	 * Configure whether to permit deletion of branches from the
 	 * {@code refs/heads/} namespace.
 	 *
 	 * @param canDelete
 	 *            {@code true} to permit deletion of branches from the
 	 *            {@code refs/heads/} namespace.
 	 * @since 3.6
 	 */
 	public void setAllowBranchDeletes(boolean canDelete) {
 		allowBranchDeletes = canDelete;
 	}
 
 	/**
 	 * Whether the client can request non-fast-forward updates of a ref,
 	 * possibly making objects unreachable.
 	 *
 	 * @return {@code true} if the client can request non-fast-forward updates
 	 *         of a ref, possibly making objects unreachable.
 	 */
 	public boolean isAllowNonFastForwards() {
 		return allowNonFastForwards;
 	}
 
 	/**
 	 * Configure whether to permit the client to ask for non-fast-forward
 	 * updates of an existing ref.
 	 *
 	 * @param canRewind
 	 *            {@code true} to permit the client to ask for non-fast-forward
 	 *            updates of an existing ref.
 	 */
 	public void setAllowNonFastForwards(boolean canRewind) {
 		allowNonFastForwards = canRewind;
 	}
 
 	/**
 	 * Whether the client's commands should be performed as a single atomic
 	 * transaction.
 	 *
 	 * @return {@code true} if the client's commands should be performed as a
 	 *         single atomic transaction.
 	 * @since 4.4
 	 */
 	public boolean isAtomic() {
 		return atomic;
 	}
 
 	/**
 	 * Configure whether to perform the client's commands as a single atomic
 	 * transaction.
 	 *
 	 * @param atomic
 	 *            {@code true} to perform the client's commands as a single
 	 *            atomic transaction.
 	 * @since 4.4
 	 */
 	public void setAtomic(boolean atomic) {
 		this.atomic = atomic;
 	}
 
 	/**
 	 * Get identity of the user making the changes in the reflog.
 	 *
 	 * @return identity of the user making the changes in the reflog.
 	 */
 	public PersonIdent getRefLogIdent() {
 		return refLogIdent;
 	}
 
 	/**
 	 * Set the identity of the user appearing in the affected reflogs.
 	 * <p>
 	 * The timestamp portion of the identity is ignored. A new identity with the
 	 * current timestamp will be created automatically when the updates occur
 	 * and the log records are written.
 	 *
 	 * @param pi
 	 *            identity of the user. If null the identity will be
 	 *            automatically determined based on the repository
 	 *            configuration.
 	 */
 	public void setRefLogIdent(PersonIdent pi) {
 		refLogIdent = pi;
 	}
 
 	/**
 	 * 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
 	 *
 	 * @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 org.eclipse.jgit.transport.AdvertiseRefsHook} chooses to
 	 * call {@link #setAdvertisedRefs(Map,Set)}, only refs set by this hook
 	 * <em>and</em> selected by the {@link org.eclipse.jgit.transport.RefFilter}
 	 * will be shown to the client. Clients may still attempt to create or
 	 * update a reference not advertised by the configured
 	 * {@link org.eclipse.jgit.transport.AdvertiseRefsHook}. These attempts
 	 * should be rejected by a matching
 	 * {@link org.eclipse.jgit.transport.PreReceiveHook}.
 	 *
 	 * @param advertiseRefsHook
 	 *            the hook; may be null to show all refs.
 	 */
 	public void setAdvertiseRefsHook(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 shown to the client. The filter
 	 * is run against the refs specified by the
 	 * {@link org.eclipse.jgit.transport.AdvertiseRefsHook} (if applicable).
 	 *
 	 * @param refFilter
 	 *            the filter; may be null to show all refs.
 	 */
 	public void setRefFilter(RefFilter refFilter) {
 		this.refFilter = refFilter != null ? refFilter : RefFilter.DEFAULT;
 	}
 
 	/**
 	 * 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.
 	 *
 	 * @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;
 	}
 
 	/**
 	 * Set the maximum number of command bytes to read from the client.
 	 *
 	 * @param limit
 	 *            command limit in bytes; if 0 there is no limit.
 	 * @since 4.7
 	 */
 	public void setMaxCommandBytes(long limit) {
 		maxCommandBytes = limit;
 	}
 
 	/**
 	 * Set the maximum number of command bytes to discard from the client.
 	 * <p>
 	 * Discarding remaining bytes allows this instance to consume the rest of
 	 * the command block and send a human readable over-limit error via the
 	 * side-band channel. If the client sends an excessive number of bytes this
 	 * limit kicks in and the instance disconnects, resulting in a non-specific
 	 * 'pipe closed', 'end of stream', or similar generic error at the client.
 	 * <p>
 	 * When the limit is set to {@code -1} the implementation will default to
 	 * the larger of {@code 3 * maxCommandBytes} or {@code 3 MiB}.
 	 *
 	 * @param limit
 	 *            discard limit in bytes; if 0 there is no limit; if -1 the
 	 *            implementation tries to set a reasonable default.
 	 * @since 4.7
 	 */
 	public void setMaxCommandDiscardBytes(long limit) {
 		maxDiscardBytes = limit;
 	}
 
 	/**
 	 * Set the maximum allowed Git object size.
 	 * <p>
 	 * If an object is larger than the given size the pack-parsing will throw an
 	 * exception aborting the receive-pack operation.
 	 *
 	 * @param limit
 	 *            the Git object size limit. If zero then there is not limit.
 	 */
 	public void setMaxObjectSizeLimit(long limit) {
 		maxObjectSizeLimit = limit;
 	}
 
 	/**
 	 * Set the maximum allowed pack size.
 	 * <p>
 	 * A pack exceeding this size will be rejected.
 	 *
 	 * @param limit
 	 *            the pack size limit, in bytes
 	 * @since 3.3
 	 */
 	public void setMaxPackSizeLimit(long limit) {
 		if (limit < 0)
 			throw new IllegalArgumentException(MessageFormat.format(
 					JGitText.get().receivePackInvalidLimit, Long.valueOf(limit)));
 		maxPackSizeLimit = limit;
 	}
 
 	/**
 	 * 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 {
 		checkRequestWasRead();
 		return enabledCapabilities.contains(CAPABILITY_SIDE_BAND_64K);
 	}
 
 	/**
 	 * Whether clients may request avoiding noisy progress messages.
 	 *
 	 * @return true if clients may request avoiding noisy progress messages.
 	 * @since 4.0
 	 */
 	public boolean isAllowQuiet() {
 		return allowQuiet;
 	}
 
 	/**
 	 * Configure if clients may request the server skip noisy messages.
 	 *
 	 * @param allow
 	 *            true to allow clients to request quiet behavior; false to
 	 *            refuse quiet behavior and send messages anyway. This may be
 	 *            necessary if processing is slow and the client-server network
 	 *            connection can timeout.
 	 * @since 4.0
 	 */
 	public void setAllowQuiet(boolean allow) {
 		allowQuiet = allow;
 	}
 
 	/**
 	 * Whether the server supports receiving push options.
 	 *
 	 * @return true if the server supports receiving push options.
 	 * @since 4.5
 	 */
 	public boolean isAllowPushOptions() {
 		return allowPushOptions;
 	}
 
 	/**
 	 * Configure if the server supports receiving push options.
 	 *
 	 * @param allow
 	 *            true to optionally accept option strings from the client.
 	 * @since 4.5
 	 */
 	public void setAllowPushOptions(boolean allow) {
 		allowPushOptions = allow;
 	}
 
 	/**
 	 * True if the client wants less verbose output.
 	 *
 	 * @return true if the client has requested the server to be less verbose.
 	 * @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.
 	 * @since 4.0
 	 */
 	public boolean isQuiet() throws RequestNotYetReadException {
 		checkRequestWasRead();
 		return quiet;
 	}
 
 	/**
 	 * Set the configuration for push certificate verification.
 	 *
 	 * @param cfg
 	 *            new configuration; if this object is null or its {@link
 	 *            SignedPushConfig#getCertNonceSeed()} is null, push certificate
 	 *            verification will be disabled.
 	 * @since 4.1
 	 */
 	public void setSignedPushConfig(SignedPushConfig cfg) {
 		signedPushConfig = cfg;
 	}
 
 	private PushCertificateParser getPushCertificateParser() {
 		if (pushCertificateParser == null) {
 			pushCertificateParser = new PushCertificateParser(db, signedPushConfig);
 		}
 		return pushCertificateParser;
 	}
 
 	/**
 	 * 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(enabledCapabilities, userAgent);
 	}
 
 	/**
 	 * Get all of the command received by the current request.
 	 *
 	 * @return all of the command received by the current request.
 	 */
 	public List<ReceiveCommand> getAllCommands() {
 		return Collections.unmodifiableList(commands);
 	}
 
 	/**
 	 * Send an error message to the client.
 	 * <p>
 	 * If any error messages are sent before the references are advertised to
 	 * the client, the errors will be sent instead of the advertisement and the
 	 * receive operation will be aborted. All clients should receive and display
 	 * such early stage errors.
 	 * <p>
 	 * If the reference advertisements have already been sent, messages are sent
 	 * in a side channel. If the client doesn't support receiving messages, the
 	 * message will be discarded, with no other indication to the caller or to
 	 * the client.
 	 * <p>
 	 * {@link org.eclipse.jgit.transport.PreReceiveHook}s should always try to
 	 * use
 	 * {@link org.eclipse.jgit.transport.ReceiveCommand#setResult(Result, String)}
 	 * with a result status of
 	 * {@link org.eclipse.jgit.transport.ReceiveCommand.Result#REJECTED_OTHER_REASON}
 	 * to indicate any reasons for rejecting an update. Messages attached to a
 	 * command are much more likely to be returned 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.
 	 */
 	public void sendError(String what) {
 		if (refs == null) {
 			if (advertiseError == null)
 				advertiseError = new StringBuilder();
 			advertiseError.append(what).append('\n');
 		} else {
 			msgOutWrapper.write(Constants.encode("error: " + what + "\n")); //$NON-NLS-1$ //$NON-NLS-2$
 		}
 	}
 
 	private void fatalError(String msg) {
 		if (errOut != null) {
 			try {
 				errOut.write(Constants.encode(msg));
 				errOut.flush();
 			} catch (IOException e) {
 				// Ignore write failures
 			}
 		} else {
 			sendError(msg);
 		}
 	}
 
 	/**
 	 * 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.
 	 */
 	public void sendMessage(String what) {
 		msgOutWrapper.write(Constants.encode(what + "\n")); //$NON-NLS-1$
 	}
 
 	/**
 	 * Get an underlying stream for sending messages to the client.
 	 *
 	 * @return an underlying stream for sending messages to the client.
 	 */
 	public OutputStream getMessageOutputStream() {
 		return msgOutWrapper;
 	}
 
 	/**
 	 * Get the size of the received pack file including the index size.
 	 *
 	 * This can only be called if the pack is already received.
 	 *
 	 * @return the size of the received pack including index size
 	 * @throws java.lang.IllegalStateException
 	 *             if called before the pack has been received
 	 * @since 3.3
 	 */
 	public long getPackSize() {
 		if (packSize != null)
 			return packSize.longValue();
 		throw new IllegalStateException(JGitText.get().packSizeNotSetYet);
 	}
 
 	/**
 	 * Get the commits from the client's shallow file.
 	 *
 	 * @return if the client is a shallow repository, the list of edge commits
 	 *     that define the client's shallow boundary. Empty set if the client
 	 *     is earlier than Git 1.9, or is a full clone.
 	 * @since 3.5
 	 */
 	protected Set<ObjectId> getClientShallowCommits() {
 		return clientShallowCommits;
 	}
 
 	/**
 	 * Whether any commands to be executed have been read.
 	 *
 	 * @return {@code true} if any commands to be executed have been read.
 	 */
 	protected boolean hasCommands() {
 		return !commands.isEmpty();
 	}
 
 	/**
 	 * Whether an error occurred that should be advertised.
 	 *
 	 * @return true if an error occurred that should be advertised.
 	 */
 	protected boolean hasError() {
 		return advertiseError != null;
 	}
 
 	/**
 	 * Initialize the instance with the given streams.
 	 *
 	 * @param input
 	 *            raw input to read client commands and pack data from. Caller
 	 *            must ensure the input is buffered, otherwise read performance
 	 *            may suffer.
 	 * @param output
 	 *            response back to the Git network client. 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.
 	 */
 	protected void init(final InputStream input, final OutputStream output,
 			final OutputStream messages) {
 		origOut = output;
 		rawIn = input;
 		rawOut = output;
 		msgOut = messages;
 
 		if (timeout > 0) {
 			final Thread caller = Thread.currentThread();
 			timer = new InterruptTimer(caller.getName() + "-Timer"); //$NON-NLS-1$
 			timeoutIn = new TimeoutInputStream(rawIn, timer);
 			TimeoutOutputStream o = new TimeoutOutputStream(rawOut, timer);
 			timeoutIn.setTimeout(timeout * 1000);
 			o.setTimeout(timeout * 1000);
 			rawIn = timeoutIn;
 			rawOut = o;
 		}
 
 		pckIn = new PacketLineIn(rawIn);
 		pckOut = new PacketLineOut(rawOut);
 		pckOut.setFlushOnEnd(false);
 
 		enabledCapabilities = new HashSet<>();
 		commands = new ArrayList<>();
 	}
 
 	/**
 	 * Get advertised refs, or the default if not explicitly advertised.
 	 *
 	 * @return advertised refs, or the default if not explicitly advertised.
 	 */
 	protected Map<String, Ref> getAdvertisedOrDefaultRefs() {
 		if (refs == null)
 			setAdvertisedRefs(null, null);
 		return refs;
 	}
 
 	/**
 	 * Receive a pack from the stream and check connectivity if necessary.
 	 *
 	 * @throws java.io.IOException
 	 *             an error occurred during unpacking or connectivity checking.
 	 */
 	protected void receivePackAndCheckConnectivity() throws IOException {
 		receivePack();
 		if (needCheckConnectivity()) {
 			checkSubmodules();
 			checkConnectivity();
 		}
 		parser = null;
 	}
 
 	/**
 	 * Unlock the pack written by this object.
 	 *
 	 * @throws java.io.IOException
 	 *             the pack could not be unlocked.
 	 */
 	protected void unlockPack() throws IOException {
 		if (packLock != null) {
 			packLock.unlock();
 			packLock = null;
 		}
 	}
 
 	/**
 	 * 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 {
 		if (advertiseError != null) {
 			adv.writeOne("ERR " + advertiseError); //$NON-NLS-1$
 			return;
 		}
 
 		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(CAPABILITY_SIDE_BAND_64K);
 		adv.advertiseCapability(CAPABILITY_DELETE_REFS);
 		adv.advertiseCapability(CAPABILITY_REPORT_STATUS);
 		if (allowQuiet)
 			adv.advertiseCapability(CAPABILITY_QUIET);
 		String nonce = getPushCertificateParser().getAdvertiseNonce();
 		if (nonce != null) {
 			adv.advertiseCapability(nonce);
 		}
 		if (db.getRefDatabase().performsAtomicTransactions())
 			adv.advertiseCapability(CAPABILITY_ATOMIC);
 		if (allowOfsDelta)
 			adv.advertiseCapability(CAPABILITY_OFS_DELTA);
 		if (allowPushOptions) {
 			adv.advertiseCapability(CAPABILITY_PUSH_OPTIONS);
 		}
 		adv.advertiseCapability(OPTION_AGENT, UserAgent.get());
 		adv.send(getAdvertisedOrDefaultRefs().values());
 		for (ObjectId obj : advertisedHaves)
 			adv.advertiseHave(obj);
 		if (adv.isEmpty())
 			adv.advertiseId(ObjectId.zeroId(), "capabilities^{}"); //$NON-NLS-1$
 		adv.end();
 	}
 
 	/**
 	 * Returns the statistics on the received pack if available. This should be
 	 * called after {@link #receivePack} is called.
 	 *
 	 * @return ReceivedPackStatistics
 	 * @since 4.6
 	 */
 	@Nullable
 	public ReceivedPackStatistics getReceivedPackStatistics() {
 		return stats;
 	}
 
 	/**
 	 * Receive a list of commands from the input.
 	 *
 	 * @throws java.io.IOException
 	 */
 	protected void recvCommands() throws IOException {
 		PacketLineIn pck = maxCommandBytes > 0
 				? new PacketLineIn(rawIn, maxCommandBytes)
 				: pckIn;
 		PushCertificateParser certParser = getPushCertificateParser();
 		boolean firstPkt = true;
 		try {
 			for (;;) {
 				String line;
 				try {
 					line = pck.readString();
 				} catch (EOFException eof) {
 					if (commands.isEmpty())
 						return;
 					throw eof;
 				}
 				if (PacketLineIn.isEnd(line)) {
 					break;
 				}
 
 				if (line.length() >= 48 && line.startsWith("shallow ")) { //$NON-NLS-1$
 					parseShallow(line.substring(8, 48));
 					continue;
 				}
 
 				if (firstPkt) {
 					firstPkt = false;
 					FirstCommand firstLine = FirstCommand.fromLine(line);
 					enabledCapabilities = firstLine.getCapabilities();
 					line = firstLine.getLine();
 					enableCapabilities();
 
 					if (line.equals(GitProtocolConstants.OPTION_PUSH_CERT)) {
 						certParser.receiveHeader(pck, !isBiDirectionalPipe());
 						continue;
 					}
 				}
 
 				if (line.equals(PushCertificateParser.BEGIN_SIGNATURE)) {
 					certParser.receiveSignature(pck);
 					continue;
 				}
 
 				ReceiveCommand cmd = parseCommand(line);
 				if (cmd.getRefName().equals(Constants.HEAD)) {
 					cmd.setResult(Result.REJECTED_CURRENT_BRANCH);
 				} else {
 					cmd.setRef(refs.get(cmd.getRefName()));
 				}
 				commands.add(cmd);
 				if (certParser.enabled()) {
 					certParser.addCommand(cmd);
 				}
 			}
 			pushCert = certParser.build();
 			if (hasCommands()) {
 				readPostCommands(pck);
 			}
 		} catch (PackProtocolException e) {
 			discardCommands();
 			fatalError(e.getMessage());
 			throw e;
 		} catch (InputOverLimitIOException e) {
 			String msg = JGitText.get().tooManyCommands;
 			discardCommands();
 			fatalError(msg);
 			throw new PackProtocolException(msg);
 		}
 	}
 
 	private void discardCommands() {
 		if (sideBand) {
 			long max = maxDiscardBytes;
 			if (max < 0) {
 				max = Math.max(3 * maxCommandBytes, 3L << 20);
 			}
 			try {
 				new PacketLineIn(rawIn, max).discardUntilEnd();
 			} catch (IOException e) {
 				// Ignore read failures attempting to discard.
 			}
 		}
 	}
 
 	private void parseShallow(String idStr) throws PackProtocolException {
 		ObjectId id;
 		try {
 			id = ObjectId.fromString(idStr);
 		} catch (InvalidObjectIdException e) {
 			throw new PackProtocolException(e.getMessage(), e);
 		}
 		clientShallowCommits.add(id);
 	}
 
 	static ReceiveCommand parseCommand(String line) throws PackProtocolException {
           if (line == null || line.length() < 83) {
 			throw new PackProtocolException(
 					JGitText.get().errorInvalidProtocolWantedOldNewRef);
 		}
 		String oldStr = line.substring(0, 40);
 		String newStr = line.substring(41, 81);
 		ObjectId oldId, newId;
 		try {
 			oldId = ObjectId.fromString(oldStr);
 			newId = ObjectId.fromString(newStr);
 		} catch (InvalidObjectIdException e) {
 			throw new PackProtocolException(
 					JGitText.get().errorInvalidProtocolWantedOldNewRef, e);
 		}
 		String name = line.substring(82);
 		if (!Repository.isValidRefName(name)) {
 			throw new PackProtocolException(
 					JGitText.get().errorInvalidProtocolWantedOldNewRef);
 		}
 		return new ReceiveCommand(oldId, newId, name);
 	}
 
 	/**
 	 * @param in
 	 *            request stream.
 	 * @throws IOException
 	 *             request line cannot be read.
 	 */
 	void readPostCommands(PacketLineIn in) throws IOException {
 		// Do nothing by default.
 	}
 
 	/**
 	 * Enable capabilities based on a previously read capabilities line.
 	 */
 	protected void enableCapabilities() {
 		sideBand = isCapabilityEnabled(CAPABILITY_SIDE_BAND_64K);
 		quiet = allowQuiet && isCapabilityEnabled(CAPABILITY_QUIET);
 		if (sideBand) {
 			OutputStream out = rawOut;
 
 			rawOut = new SideBandOutputStream(CH_DATA, MAX_BUF, out);
 			msgOut = new SideBandOutputStream(CH_PROGRESS, MAX_BUF, out);
 			errOut = new SideBandOutputStream(CH_ERROR, MAX_BUF, out);
 
 			pckOut = new PacketLineOut(rawOut);
 			pckOut.setFlushOnEnd(false);
 		}
 	}
 
 	/**
 	 * Check if the peer requested a capability.
 	 *
 	 * @param name
 	 *            protocol name identifying the capability.
 	 * @return true if the peer requested the capability to be enabled.
 	 */
 	protected boolean isCapabilityEnabled(String name) {
 		return enabledCapabilities.contains(name);
 	}
 
 	void checkRequestWasRead() {
 		if (enabledCapabilities == null)
 			throw new RequestNotYetReadException();
 	}
 
 	/**
 	 * Whether a pack is expected based on the list of commands.
 	 *
 	 * @return {@code true} if a pack is expected based on the list of commands.
 	 */
 	protected boolean needPack() {
 		for (ReceiveCommand cmd : commands) {
 			if (cmd.getType() != ReceiveCommand.Type.DELETE)
 				return true;
 		}
 		return false;
 	}
 
 	/**
 	 * Receive a pack from the input and store it in the repository.
 	 *
 	 * @throws IOException
 	 *             an error occurred reading or indexing the pack.
 	 */
 	private void receivePack() throws IOException {
 		// It might take the client a while to pack the objects it needs
 		// to send to us.  We should increase our timeout so we don't
 		// abort while the client is computing.
 		//
 		if (timeoutIn != null)
 			timeoutIn.setTimeout(10 * timeout * 1000);
 
 		ProgressMonitor receiving = NullProgressMonitor.INSTANCE;
 		ProgressMonitor resolving = NullProgressMonitor.INSTANCE;
 		if (sideBand && !quiet)
 			resolving = new SideBandProgressMonitor(msgOut);
 
 		try (ObjectInserter ins = db.newObjectInserter()) {
 			String lockMsg = "jgit receive-pack"; //$NON-NLS-1$
 			if (getRefLogIdent() != null)
 				lockMsg += " from " + getRefLogIdent().toExternalString(); //$NON-NLS-1$
 
 			parser = ins.newPackParser(packInputStream());
 			parser.setAllowThin(true);
 			parser.setNeedNewObjectIds(checkReferencedIsReachable);
 			parser.setNeedBaseObjectIds(checkReferencedIsReachable);
 			parser.setCheckEofAfterPackFooter(!biDirectionalPipe
 					&& !isExpectDataAfterPackFooter());
 			parser.setExpectDataAfterPackFooter(isExpectDataAfterPackFooter());
 			parser.setObjectChecker(objectChecker);
 			parser.setLockMessage(lockMsg);
 			parser.setMaxObjectSizeLimit(maxObjectSizeLimit);
 			packLock = parser.parse(receiving, resolving);
 			packSize = Long.valueOf(parser.getPackSize());
 			stats = parser.getReceivedPackStatistics();
 			ins.flush();
 		}
 
 		if (timeoutIn != null)
 			timeoutIn.setTimeout(timeout * 1000);
 	}
 
 	private InputStream packInputStream() {
 		InputStream packIn = rawIn;
 		if (maxPackSizeLimit >= 0) {
 			packIn = new LimitedInputStream(packIn, maxPackSizeLimit) {
 				@Override
 				protected void limitExceeded() throws TooLargePackException {
 					throw new TooLargePackException(limit);
 				}
 			};
 		}
 		return packIn;
 	}
 
 	private boolean needCheckConnectivity() {
 		return isCheckReceivedObjects()
 				|| isCheckReferencedObjectsAreReachable()
 				|| !getClientShallowCommits().isEmpty();
 	}
 
 	private void checkSubmodules()
 			throws IOException {
 		ObjectDatabase odb = db.getObjectDatabase();
 		if (objectChecker == null) {
 			return;
 		}
 		for (GitmoduleEntry entry : objectChecker.getGitsubmodules()) {
 			AnyObjectId blobId = entry.getBlobId();
 			ObjectLoader blob = odb.open(blobId, Constants.OBJ_BLOB);
 
 			try {
 				SubmoduleValidator.assertValidGitModulesFile(
 						new String(blob.getBytes(), UTF_8));
 			} catch (LargeObjectException | SubmoduleValidationException e) {
 				throw new IOException(e);
 			}
 		}
 	}
 
 	private void checkConnectivity() throws IOException {
 		ObjectIdSubclassMap<ObjectId> baseObjects = null;
 		ObjectIdSubclassMap<ObjectId> providedObjects = null;
 		ProgressMonitor checking = NullProgressMonitor.INSTANCE;
 		if (sideBand && !quiet) {
 			SideBandProgressMonitor m = new SideBandProgressMonitor(msgOut);
 			m.setDelayStart(750, TimeUnit.MILLISECONDS);
 			checking = m;
 		}
 
 		if (checkReferencedIsReachable) {
 			baseObjects = parser.getBaseObjectIds();
 			providedObjects = parser.getNewObjectIds();
 		}
 		parser = null;
 
 		try (ObjectWalkectWalk.html#ObjectWalk">ObjectWalk ow = new ObjectWalk(db)) {
 			if (baseObjects != null) {
 				ow.sort(RevSort.TOPO);
 				if (!baseObjects.isEmpty())
 					ow.sort(RevSort.BOUNDARY, true);
 			}
 
 			for (ReceiveCommand cmd : commands) {
 				if (cmd.getResult() != Result.NOT_ATTEMPTED)
 					continue;
 				if (cmd.getType() == ReceiveCommand.Type.DELETE)
 					continue;
 				ow.markStart(ow.parseAny(cmd.getNewId()));
 			}
 			for (ObjectId have : advertisedHaves) {
 				RevObject o = ow.parseAny(have);
 				ow.markUninteresting(o);
 
 				if (baseObjects != null && !baseObjects.isEmpty()) {
 					o = ow.peel(o);
 					if (o instanceof RevCommit)
 						o = ((RevCommit) o).getTree();
 					if (o instanceof RevTree)
 						ow.markUninteresting(o);
 				}
 			}
 
 			checking.beginTask(JGitText.get().countingObjects,
 					ProgressMonitor.UNKNOWN);
 			RevCommit c;
 			while ((c = ow.next()) != null) {
 				checking.update(1);
 				if (providedObjects != null //
 						&& !c.has(RevFlag.UNINTERESTING) //
 						&& !providedObjects.contains(c))
 					throw new MissingObjectException(c, Constants.TYPE_COMMIT);
 			}
 
 			RevObject o;
 			while ((o = ow.nextObject()) != null) {
 				checking.update(1);
 				if (o.has(RevFlag.UNINTERESTING))
 					continue;
 
 				if (providedObjects != null) {
 					if (providedObjects.contains(o))
 						continue;
 					else
 						throw new MissingObjectException(o, o.getType());
 				}
 
 				if (o instanceof RevBlob && !db.getObjectDatabase().has(o))
 					throw new MissingObjectException(o, Constants.TYPE_BLOB);
 			}
 			checking.endTask();
 
 			if (baseObjects != null) {
 				for (ObjectId id : baseObjects) {
 					o = ow.parseAny(id);
 					if (!o.has(RevFlag.UNINTERESTING))
 						throw new MissingObjectException(o, o.getType());
 				}
 			}
 		}
 	}
 
 	/**
 	 * Validate the command list.
 	 */
 	protected void validateCommands() {
 		for (ReceiveCommand cmd : commands) {
 			final Ref ref = cmd.getRef();
 			if (cmd.getResult() != Result.NOT_ATTEMPTED)
 				continue;
 
 			if (cmd.getType() == ReceiveCommand.Type.DELETE) {
 				if (!isAllowDeletes()) {
 					// Deletes are not supported on this repository.
 					cmd.setResult(Result.REJECTED_NODELETE);
 					continue;
 				}
 				if (!isAllowBranchDeletes()
 						&& ref.getName().startsWith(Constants.R_HEADS)) {
 					// Branches cannot be deleted, but other refs can.
 					cmd.setResult(Result.REJECTED_NODELETE);
 					continue;
 				}
 			}
 
 			if (cmd.getType() == ReceiveCommand.Type.CREATE) {
 				if (!isAllowCreates()) {
 					cmd.setResult(Result.REJECTED_NOCREATE);
 					continue;
 				}
 
 				if (ref != null && !isAllowNonFastForwards()) {
 					// Creation over an existing ref is certainly not going
 					// to be a fast-forward update. We can reject it early.
 					//
 					cmd.setResult(Result.REJECTED_NONFASTFORWARD);
 					continue;
 				}
 
 				if (ref != null) {
 					// A well behaved client shouldn't have sent us a
 					// create command for a ref we advertised to it.
 					//
 					cmd.setResult(Result.REJECTED_OTHER_REASON,
 							JGitText.get().refAlreadyExists);
 					continue;
 				}
 			}
 
 			if (cmd.getType() == ReceiveCommand.Type.DELETE && ref != null) {
 				ObjectId id = ref.getObjectId();
 				if (id == null) {
 					id = ObjectId.zeroId();
 				}
 				if (!ObjectId.zeroId().equals(cmd.getOldId())
 						&& !id.equals(cmd.getOldId())) {
 					// Delete commands can be sent with the old id matching our
 					// advertised value, *OR* with the old id being 0{40}. Any
 					// other requested old id is invalid.
 					//
 					cmd.setResult(Result.REJECTED_OTHER_REASON,
 							JGitText.get().invalidOldIdSent);
 					continue;
 				}
 			}
 
 			if (cmd.getType() == ReceiveCommand.Type.UPDATE) {
 				if (ref == null) {
 					// The ref must have been advertised in order to be updated.
 					//
 					cmd.setResult(Result.REJECTED_OTHER_REASON, JGitText.get().noSuchRef);
 					continue;
 				}
 				ObjectId id = ref.getObjectId();
 				if (id == null) {
 					// We cannot update unborn branch
 					cmd.setResult(Result.REJECTED_OTHER_REASON,
 							JGitText.get().cannotUpdateUnbornBranch);
 					continue;
 				}
 
 				if (!id.equals(cmd.getOldId())) {
 					// A properly functioning client will send the same
 					// object id we advertised.
 					//
 					cmd.setResult(Result.REJECTED_OTHER_REASON,
 							JGitText.get().invalidOldIdSent);
 					continue;
 				}
 
 				// Is this possibly a non-fast-forward style update?
 				//
 				RevObject oldObj, newObj;
 				try {
 					oldObj = walk.parseAny(cmd.getOldId());
 				} catch (IOException e) {
 					cmd.setResult(Result.REJECTED_MISSING_OBJECT, cmd
 							.getOldId().name());
 					continue;
 				}
 
 				try {
 					newObj = walk.parseAny(cmd.getNewId());
 				} catch (IOException e) {
 					cmd.setResult(Result.REJECTED_MISSING_OBJECT, cmd
 							.getNewId().name());
 					continue;
 				}
 
 				if (oldObj instanceof RevCommite/jgit/revwalk/RevCommit.html#RevCommit">RevCommit && newObj instanceof RevCommit) {
 					try {
 						if (walk.isMergedInto((RevCommit) oldObj,
 								(RevCommit) newObj))
 							cmd.setTypeFastForwardUpdate();
 						else
 							cmd.setType(ReceiveCommand.Type.UPDATE_NONFASTFORWARD);
 					} catch (MissingObjectException e) {
 						cmd.setResult(Result.REJECTED_MISSING_OBJECT, e
 								.getMessage());
 					} catch (IOException e) {
 						cmd.setResult(Result.REJECTED_OTHER_REASON);
 					}
 				} else {
 					cmd.setType(ReceiveCommand.Type.UPDATE_NONFASTFORWARD);
 				}
 
 				if (cmd.getType() == ReceiveCommand.Type.UPDATE_NONFASTFORWARD
 						&& !isAllowNonFastForwards()) {
 					cmd.setResult(Result.REJECTED_NONFASTFORWARD);
 					continue;
 				}
 			}
 
 			if (!cmd.getRefName().startsWith(Constants.R_REFS)
 					|| !Repository.isValidRefName(cmd.getRefName())) {
 				cmd.setResult(Result.REJECTED_OTHER_REASON, JGitText.get().funnyRefname);
 			}
 		}
 	}
 
 	/**
 	 * Whether any commands have been rejected so far.
 	 *
 	 * @return if any commands have been rejected so far.
 	 * @since 3.6
 	 */
 	protected boolean anyRejects() {
 		for (ReceiveCommand cmd : commands) {
 			if (cmd.getResult() != Result.NOT_ATTEMPTED && cmd.getResult() != Result.OK)
 				return true;
 		}
 		return false;
 	}
 
 	/**
 	 * Set the result to fail for any command that was not processed yet.
 	 *
 	 * @since 3.6
 	 */
 	protected void failPendingCommands() {
 		ReceiveCommand.abort(commands);
 	}
 
 	/**
 	 * Filter the list of commands according to result.
 	 *
 	 * @param want
 	 *            desired status to filter by.
 	 * @return a copy of the command list containing only those commands with the
 	 *         desired status.
 	 */
 	protected List<ReceiveCommand> filterCommands(Result want) {
 		return ReceiveCommand.filter(commands, want);
 	}
 
 	/**
 	 * Execute commands to update references.
 	 */
 	protected void executeCommands() {
 		List<ReceiveCommand> toApply = filterCommands(Result.NOT_ATTEMPTED);
 		if (toApply.isEmpty())
 			return;
 
 		ProgressMonitor updating = NullProgressMonitor.INSTANCE;
 		if (sideBand) {
 			SideBandProgressMonitor pm = new SideBandProgressMonitor(msgOut);
 			pm.setDelayStart(250, TimeUnit.MILLISECONDS);
 			updating = pm;
 		}
 
 		BatchRefUpdate batch = db.getRefDatabase().newBatchUpdate();
 		batch.setAllowNonFastForwards(isAllowNonFastForwards());
 		batch.setAtomic(isAtomic());
 		batch.setRefLogIdent(getRefLogIdent());
 		batch.setRefLogMessage("push", true); //$NON-NLS-1$
 		batch.addCommand(toApply);
 		try {
 			batch.setPushCertificate(getPushCertificate());
 			batch.execute(walk, updating);
 		} catch (IOException err) {
 			for (ReceiveCommand cmd : toApply) {
 				if (cmd.getResult() == Result.NOT_ATTEMPTED)
 					cmd.reject(err);
 			}
 		}
 	}
 
 	/**
 	 * Send a status report.
 	 *
 	 * @param forClient
 	 *            true if this report is for a Git client, false if it is for an
 	 *            end-user.
 	 * @param unpackError
 	 *            an error that occurred during unpacking, or {@code null}
 	 * @param out
 	 *            the reporter for sending the status strings.
 	 * @throws java.io.IOException
 	 *             an error occurred writing the status report.
 	 */
 	protected void sendStatusReport(final boolean forClient,
 			final Throwable unpackError, final Reporter out) throws IOException {
 		if (unpackError != null) {
 			out.sendString("unpack error " + unpackError.getMessage()); //$NON-NLS-1$
 			if (forClient) {
 				for (ReceiveCommand cmd : commands) {
 					out.sendString("ng " + cmd.getRefName() //$NON-NLS-1$
 							+ " n/a (unpacker error)"); //$NON-NLS-1$
 				}
 			}
 			return;
 		}
 
 		if (forClient)
 			out.sendString("unpack ok"); //$NON-NLS-1$
 		for (ReceiveCommand cmd : commands) {
 			if (cmd.getResult() == Result.OK) {
 				if (forClient)
 					out.sendString("ok " + cmd.getRefName()); //$NON-NLS-1$
 				continue;
 			}
 
 			final StringBuilder r = new StringBuilder();
 			if (forClient)
 				r.append("ng ").append(cmd.getRefName()).append(" "); //$NON-NLS-1$ //$NON-NLS-2$
 			else
 				r.append(" ! [rejected] ").append(cmd.getRefName()).append(" ("); //$NON-NLS-1$ //$NON-NLS-2$
 
 			switch (cmd.getResult()) {
 			case NOT_ATTEMPTED:
 				r.append("server bug; ref not processed"); //$NON-NLS-1$
 				break;
 
 			case REJECTED_NOCREATE:
 				r.append("creation prohibited"); //$NON-NLS-1$
 				break;
 
 			case REJECTED_NODELETE:
 				r.append("deletion prohibited"); //$NON-NLS-1$
 				break;
 
 			case REJECTED_NONFASTFORWARD:
 				r.append("non-fast forward"); //$NON-NLS-1$
 				break;
 
 			case REJECTED_CURRENT_BRANCH:
 				r.append("branch is currently checked out"); //$NON-NLS-1$
 				break;
 
 			case REJECTED_MISSING_OBJECT:
 				if (cmd.getMessage() == null)
 					r.append("missing object(s)"); //$NON-NLS-1$
 				else if (cmd.getMessage().length() == Constants.OBJECT_ID_STRING_LENGTH) {
 					r.append("object "); //$NON-NLS-1$
 					r.append(cmd.getMessage());
 					r.append(" missing"); //$NON-NLS-1$
 				} else
 					r.append(cmd.getMessage());
 				break;
 
 			case REJECTED_OTHER_REASON:
 				if (cmd.getMessage() == null)
 					r.append("unspecified reason"); //$NON-NLS-1$
 				else
 					r.append(cmd.getMessage());
 				break;
 
 			case LOCK_FAILURE:
 				r.append("failed to lock"); //$NON-NLS-1$
 				break;
 
 			case OK:
 				// We shouldn't have reached this case (see 'ok' case above).
 				continue;
 			}
 			if (!forClient)
 				r.append(")"); //$NON-NLS-1$
 			out.sendString(r.toString());
 		}
 	}
 
 	/**
 	 * Close and flush (if necessary) the underlying streams.
 	 *
 	 * @throws java.io.IOException
 	 */
 	protected void close() throws IOException {
 		if (sideBand) {
 			// If we are using side band, we need to send a final
 			// flush-pkt to tell the remote peer the side band is
 			// complete and it should stop decoding. We need to
 			// use the original output stream as rawOut is now the
 			// side band data channel.
 			//
 			((SideBandOutputStream) msgOut).flushBuffer();
 			((SideBandOutputStream) rawOut).flushBuffer();
 
 			PacketLineOut plo = new PacketLineOut(origOut);
 			plo.setFlushOnEnd(false);
 			plo.end();
 		}
 
 		if (biDirectionalPipe) {
 			// If this was a native git connection, flush the pipe for
 			// the caller. For smart HTTP we don't do this flush and
 			// instead let the higher level HTTP servlet code do it.
 			//
 			if (!sideBand && msgOut != null)
 				msgOut.flush();
 			rawOut.flush();
 		}
 	}
 
 	/**
 	 * Release any resources used by this object.
 	 *
 	 * @throws java.io.IOException
 	 *             the pack could not be unlocked.
 	 */
 	protected void release() throws IOException {
 		walk.close();
 		unlockPack();
 		timeoutIn = null;
 		rawIn = null;
 		rawOut = null;
 		msgOut = null;
 		pckIn = null;
 		pckOut = null;
 		refs = null;
 		// Keep the capabilities. If responses are sent after this release
 		// we need to remember at least whether sideband communication has to be
 		// used
 		commands = null;
 		if (timer != null) {
 			try {
 				timer.terminate();
 			} finally {
 				timer = null;
 			}
 		}
 	}
 
 	/** Interface for reporting status messages. */
 	static abstract class Reporter {
 			abstract void sendString(String s) throws IOException;
 	}
 }