Disambiguate pkt-line "0000" from "0004"

[egit.git] / org.spearce.jgit / src / org / spearce / jgit / transport / ReceivePack.java

/*
 * Copyright (C) 2008, Google Inc.
 *
 * 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 Git Development Community 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.spearce.jgit.transport;

import java.io.BufferedWriter;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.spearce.jgit.errors.MissingObjectException;
import org.spearce.jgit.errors.PackProtocolException;
import org.spearce.jgit.lib.Constants;
import org.spearce.jgit.lib.NullProgressMonitor;
import org.spearce.jgit.lib.ObjectId;
import org.spearce.jgit.lib.PackLock;
import org.spearce.jgit.lib.PersonIdent;
import org.spearce.jgit.lib.Ref;
import org.spearce.jgit.lib.RefComparator;
import org.spearce.jgit.lib.RefUpdate;
import org.spearce.jgit.lib.Repository;
import org.spearce.jgit.lib.RepositoryConfig;
import org.spearce.jgit.revwalk.ObjectWalk;
import org.spearce.jgit.revwalk.RevCommit;
import org.spearce.jgit.revwalk.RevObject;
import org.spearce.jgit.revwalk.RevWalk;
import org.spearce.jgit.transport.ReceiveCommand.Result;

/**
 * Implements the server side of a push connection, receiving objects.
 */
public class ReceivePack {
        static final String CAPABILITY_REPORT_STATUS = BasePackPushConnection.CAPABILITY_REPORT_STATUS;

        static final String CAPABILITY_DELETE_REFS = BasePackPushConnection.CAPABILITY_DELETE_REFS;

        static final String CAPABILITY_OFS_DELTA = BasePackPushConnection.CAPABILITY_OFS_DELTA;

        /** Database we write the stored objects into. */
        private final Repository db;

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

        /** Should an incoming transfer validate objects? */
        private boolean checkReceivedObjects;

        /** Should an incoming transfer permit create requests? */
        private boolean allowCreates;

        /** Should an incoming transfer permit delete requests? */
        private boolean allowDeletes;

        /** Should an incoming transfer permit non-fast-forward requests? */
        private boolean allowNonFastForwards;

        private boolean allowOfsDelta;

        /** Identity to record action as within the reflog. */
        private PersonIdent refLogIdent;

        /** Hook to validate the update commands before execution. */
        private PreReceiveHook preReceive;

        /** Hook to report on the commands after execution. */
        private PostReceiveHook postReceive;

        private InputStream rawIn;

        private OutputStream rawOut;

        private PacketLineIn pckIn;

        private PacketLineOut pckOut;

        private PrintWriter msgs;

        /** The refs we advertised as existing at the start of the connection. */
        private Map<String, Ref> refs;

        /** Capabilities requested by the client. */
        private Set<String> enabledCapablities;

        /** Commands to execute, as received by the client. */
        private List<ReceiveCommand> commands;

        /** An exception caught while unpacking and fsck'ing the objects. */
        private Throwable unpackError;

        /** if {@link #enabledCapablities} has {@link #CAPABILITY_REPORT_STATUS} */
        private boolean reportStatus;

        /** Lock around the received pack file, while updating refs. */
        private PackLock packLock;

        /**
         * Create a new pack receive for an open repository.
         *
         * @param into
         *            the destination repository.
         */
        public ReceivePack(final Repository into) {
                db = into;
                walk = new RevWalk(db);

                final RepositoryConfig cfg = db.getConfig();
                checkReceivedObjects = cfg.getBoolean("receive", "fsckobjects", false);
                allowCreates = true;
                allowDeletes = !cfg.getBoolean("receive", "denydeletes", false);
                allowNonFastForwards = !cfg.getBoolean("receive",
                                "denynonfastforwards", false);
                allowOfsDelta = cfg.getBoolean("repack", "usedeltabaseoffset", true);
                preReceive = PreReceiveHook.NULL;
                postReceive = PostReceiveHook.NULL;
        }

        /** @return the repository this receive completes into. */
        public final Repository getRepository() {
                return db;
        }

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

        /** @return all refs which were advertised to the client. */
        public final Map<String, Ref> getAdvertisedRefs() {
                return refs;
        }

        /**
         * @return 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 checkReceivedObjects;
        }

        /**
         * @param check
         *            true to enable checking received objects; false to assume all
         *            received objects are valid.
         */
        public void setCheckReceivedObjects(final boolean check) {
                checkReceivedObjects = check;
        }

        /** @return true if the client can request refs to be created. */
        public boolean isAllowCreates() {
                return allowCreates;
        }

        /**
         * @param canCreate
         *            true to permit create ref commands to be processed.
         */
        public void setAllowCreates(final boolean canCreate) {
                allowCreates = canCreate;
        }

        /** @return true if the client can request refs to be deleted. */
        public boolean isAllowDeletes() {
                return allowDeletes;
        }

        /**
         * @param canDelete
         *            true to permit delete ref commands to be processed.
         */
        public void setAllowDeletes(final boolean canDelete) {
                allowDeletes = canDelete;
        }

        /**
         * @return true if the client can request non-fast-forward updates of a ref,
         *         possibly making objects unreachable.
         */
        public boolean isAllowNonFastForwards() {
                return allowNonFastForwards;
        }

        /**
         * @param canRewind
         *            true to permit the client to ask for non-fast-forward updates
         *            of an existing ref.
         */
        public void setAllowNonFastForwards(final boolean canRewind) {
                allowNonFastForwards = canRewind;
        }

        /** @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(final PersonIdent pi) {
                refLogIdent = pi;
        }

        /** @return get the hook invoked before updates occur. */
        public PreReceiveHook getPreReceiveHook() {
                return preReceive;
        }

        /**
         * Set the hook which is invoked prior to commands being executed.
         * <p>
         * Only valid commands (those which have no obvious errors according to the
         * received input and this instance's configuration) are passed into the
         * hook. The hook may mark a command with a result of any value other than
         * {@link Result#NOT_ATTEMPTED} to block its execution.
         * <p>
         * The hook may be called with an empty command collection if the current
         * set is completely invalid.
         *
         * @param h
         *            the hook instance; may be null to disable the hook.
         */
        public void setPreReceiveHook(final PreReceiveHook h) {
                preReceive = h != null ? h : PreReceiveHook.NULL;
        }

        /** @return get the hook invoked after updates occur. */
        public PostReceiveHook getPostReceiveHook() {
                return postReceive;
        }

        /**
         * Set the hook which is invoked after commands are executed.
         * <p>
         * Only successful commands (type is {@link Result#OK}) are passed into the
         * hook. The hook may be called with an empty command collection if the
         * current set all resulted in an error.
         *
         * @param h
         *            the hook instance; may be null to disable the hook.
         */
        public void setPostReceiveHook(final PostReceiveHook h) {
                postReceive = h != null ? h : PostReceiveHook.NULL;
        }

        /** @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, 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.
         * <p>
         * {@link PreReceiveHook}s should always try to use
         * {@link ReceiveCommand#setResult(Result, String)} with a result status of
         * {@link 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(final String what) {
                sendMessage("error", what);
        }

        /**
         * 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(final String what) {
                sendMessage("remote", what);
        }

        private void sendMessage(final String type, final String what) {
                if (msgs != null)
                        msgs.println(type + ": " + what);
        }

        /**
         * Execute the receive task on the socket.
         *
         * @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.
         * @throws IOException
         */
        public void receive(final InputStream input, final OutputStream output,
                        final OutputStream messages) throws IOException {
                try {
                        rawIn = input;
                        rawOut = output;

                        pckIn = new PacketLineIn(rawIn);
                        pckOut = new PacketLineOut(rawOut);
                        if (messages != null) {
                                msgs = new PrintWriter(new BufferedWriter(
                                                new OutputStreamWriter(messages, Constants.CHARSET),
                                                8192)) {
                                        @Override
                                        public void println() {
                                                print('\n');
                                        }
                                };
                        }

                        enabledCapablities = new HashSet<String>();
                        commands = new ArrayList<ReceiveCommand>();

                        service();
                } finally {
                        try {
                                if (msgs != null) {
                                        msgs.flush();
                                }
                        } finally {
                                unlockPack();
                                rawIn = null;
                                rawOut = null;
                                pckIn = null;
                                pckOut = null;
                                msgs = null;
                                refs = null;
                                enabledCapablities = null;
                                commands = null;
                        }
                }
        }

        private void service() throws IOException {
                sendAdvertisedRefs();
                recvCommands();
                if (!commands.isEmpty()) {
                        enableCapabilities();

                        if (needPack()) {
                                try {
                                        receivePack();
                                        if (isCheckReceivedObjects())
                                                checkConnectivity();
                                        unpackError = null;
                                } catch (IOException err) {
                                        unpackError = err;
                                } catch (RuntimeException err) {
                                        unpackError = err;
                                } catch (Error err) {
                                        unpackError = err;
                                }
                        }

                        if (unpackError == null) {
                                validateCommands();
                                executeCommands();
                        }
                        unlockPack();

                        if (reportStatus) {
                                sendStatusReport(true, new Reporter() {
                                        void sendString(final String s) throws IOException {
                                                pckOut.writeString(s + "\n");
                                        }
                                });
                                pckOut.end();
                        } else if (msgs != null) {
                                sendStatusReport(false, new Reporter() {
                                        void sendString(final String s) throws IOException {
                                                msgs.println(s);
                                        }
                                });
                                msgs.flush();
                        }

                        postReceive.onPostReceive(this, filterCommands(Result.OK));
                }
        }

        private void unlockPack() {
                if (packLock != null) {
                        packLock.unlock();
                        packLock = null;
                }
        }

        private void sendAdvertisedRefs() throws IOException {
                refs = db.getAllRefs();

                final StringBuilder m = new StringBuilder(100);
                final char[] idtmp = new char[2 * Constants.OBJECT_ID_LENGTH];
                final Iterator<Ref> i = RefComparator.sort(refs.values()).iterator();
                {
                        if (i.hasNext()) {
                                final Ref r = i.next();
                                format(m, idtmp, r.getObjectId(), r.getOrigName());
                        } else {
                                format(m, idtmp, ObjectId.zeroId(), "capabilities^{}");
                        }
                        m.append('\0');
                        m.append(' ');
                        m.append(CAPABILITY_DELETE_REFS);
                        m.append(' ');
                        m.append(CAPABILITY_REPORT_STATUS);
                        if (allowOfsDelta) {
                                m.append(' ');
                                m.append(CAPABILITY_OFS_DELTA);
                        }
                        m.append(' ');
                        writeAdvertisedRef(m);
                }

                while (i.hasNext()) {
                        final Ref r = i.next();
                        format(m, idtmp, r.getObjectId(), r.getOrigName());
                        writeAdvertisedRef(m);
                }
                pckOut.end();
        }

        private void format(final StringBuilder m, final char[] idtmp,
                        final ObjectId id, final String name) {
                m.setLength(0);
                id.copyTo(idtmp, m);
                m.append(' ');
                m.append(name);
        }

        private void writeAdvertisedRef(final StringBuilder m) throws IOException {
                m.append('\n');
                pckOut.writeString(m.toString());
        }

        private void recvCommands() throws IOException {
                for (;;) {
                        String line;
                        try {
                                line = pckIn.readStringRaw();
                        } catch (EOFException eof) {
                                if (commands.isEmpty())
                                        return;
                                throw eof;
                        }
                        if (line == PacketLineIn.END)
                                break;

                        if (commands.isEmpty()) {
                                final int nul = line.indexOf('\0');
                                if (nul >= 0) {
                                        for (String c : line.substring(nul + 1).split(" "))
                                                enabledCapablities.add(c);
                                        line = line.substring(0, nul);
                                }
                        }

                        if (line.length() < 83) {
                                final String m = "error: invalid protocol: wanted 'old new ref'";
                                sendError(m);
                                throw new PackProtocolException(m);
                        }

                        final ObjectId oldId = ObjectId.fromString(line.substring(0, 40));
                        final ObjectId newId = ObjectId.fromString(line.substring(41, 81));
                        final String name = line.substring(82);
                        final ReceiveCommand cmd = new ReceiveCommand(oldId, newId, name);
                        cmd.setRef(refs.get(cmd.getRefName()));
                        commands.add(cmd);
                }
        }

        private void enableCapabilities() {
                reportStatus = enabledCapablities.contains(CAPABILITY_REPORT_STATUS);
        }

        private boolean needPack() {
                for (final ReceiveCommand cmd : commands) {
                        if (cmd.getType() != ReceiveCommand.Type.DELETE)
                                return true;
                }
                return false;
        }

        private void receivePack() throws IOException {
                final IndexPack ip = IndexPack.create(db, rawIn);
                ip.setFixThin(true);
                ip.setObjectChecking(isCheckReceivedObjects());
                ip.index(NullProgressMonitor.INSTANCE);

                String lockMsg = "jgit receive-pack";
                if (getRefLogIdent() != null)
                        lockMsg += " from " + getRefLogIdent().toExternalString();
                packLock = ip.renameAndOpenPack(lockMsg);
        }

        private void checkConnectivity() throws IOException {
                final ObjectWalk ow = new ObjectWalk(db);
                for (final ReceiveCommand cmd : commands) {
                        if (cmd.getResult() != Result.NOT_ATTEMPTED)
                                continue;
                        if (cmd.getType() == ReceiveCommand.Type.DELETE)
                                continue;
                        ow.markStart(ow.parseAny(cmd.getNewId()));
                }
                for (final Ref ref : refs.values())
                        ow.markUninteresting(ow.parseAny(ref.getObjectId()));
                ow.checkConnectivity();
        }

        private void validateCommands() {
                for (final ReceiveCommand cmd : commands) {
                        final Ref ref = cmd.getRef();
                        if (cmd.getResult() != Result.NOT_ATTEMPTED)
                                continue;

                        if (cmd.getType() == ReceiveCommand.Type.DELETE
                                        && !isAllowDeletes()) {
                                // Deletes are not supported on this repository.
                                //
                                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 an
                                        // update command for a ref we advertised to it.
                                        //
                                        cmd.setResult(Result.REJECTED_OTHER_REASON, "ref exists");
                                        continue;
                                }
                        }

                        if (cmd.getType() == ReceiveCommand.Type.DELETE && ref != null
                                        && !ObjectId.zeroId().equals(cmd.getOldId())
                                        && !ref.getObjectId().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,
                                                "invalid old id sent");
                                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, "no such ref");
                                        continue;
                                }

                                if (!ref.getObjectId().equals(cmd.getOldId())) {
                                        // A properly functioning client will send the same
                                        // object id we advertised.
                                        //
                                        cmd.setResult(Result.REJECTED_OTHER_REASON,
                                                        "invalid old id sent");
                                        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 RevCommit && newObj instanceof RevCommit) {
                                        try {
                                                if (!walk.isMergedInto((RevCommit) oldObj,
                                                                (RevCommit) newObj)) {
                                                        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.getRefName().startsWith(Constants.R_REFS)
                                        || !Repository.isValidRefName(cmd.getRefName())) {
                                cmd.setResult(Result.REJECTED_OTHER_REASON, "funny refname");
                        }
                }
        }

        private void executeCommands() {
                preReceive.onPreReceive(this, filterCommands(Result.NOT_ATTEMPTED));
                for (final ReceiveCommand cmd : filterCommands(Result.NOT_ATTEMPTED))
                        execute(cmd);
        }

        private void execute(final ReceiveCommand cmd) {
                try {
                        final RefUpdate ru = db.updateRef(cmd.getRefName());
                        ru.setRefLogIdent(getRefLogIdent());
                        switch (cmd.getType()) {
                        case DELETE:
                                if (!ObjectId.zeroId().equals(cmd.getOldId())) {
                                        // We can only do a CAS style delete if the client
                                        // didn't bork its delete request by sending the
                                        // wrong zero id rather than the advertised one.
                                        //
                                        ru.setExpectedOldObjectId(cmd.getOldId());
                                }
                                ru.setForceUpdate(true);
                                status(cmd, ru.delete(walk));
                                break;

                        case CREATE:
                        case UPDATE:
                        case UPDATE_NONFASTFORWARD:
                                ru.setForceUpdate(isAllowNonFastForwards());
                                ru.setExpectedOldObjectId(cmd.getOldId());
                                ru.setNewObjectId(cmd.getNewId());
                                ru.setRefLogMessage("push", true);
                                status(cmd, ru.update(walk));
                                break;
                        }
                } catch (IOException err) {
                        cmd.setResult(Result.REJECTED_OTHER_REASON, "lock error: "
                                        + err.getMessage());
                }
        }

        private void status(final ReceiveCommand cmd, final RefUpdate.Result result) {
                switch (result) {
                case NOT_ATTEMPTED:
                        cmd.setResult(Result.NOT_ATTEMPTED);
                        break;

                case LOCK_FAILURE:
                case IO_FAILURE:
                        cmd.setResult(Result.LOCK_FAILURE);
                        break;

                case NO_CHANGE:
                case NEW:
                case FORCED:
                case FAST_FORWARD:
                        cmd.setResult(Result.OK);
                        break;

                case REJECTED:
                        cmd.setResult(Result.REJECTED_NONFASTFORWARD);
                        break;

                case REJECTED_CURRENT_BRANCH:
                        cmd.setResult(Result.REJECTED_CURRENT_BRANCH);
                        break;

                default:
                        cmd.setResult(Result.REJECTED_OTHER_REASON, result.name());
                        break;
                }
        }

        private List<ReceiveCommand> filterCommands(final Result want) {
                final List<ReceiveCommand> r = new ArrayList<ReceiveCommand>(commands
                                .size());
                for (final ReceiveCommand cmd : commands) {
                        if (cmd.getResult() == want)
                                r.add(cmd);
                }
                return r;
        }

        private void sendStatusReport(final boolean forClient, final Reporter out)
                        throws IOException {
                if (unpackError != null) {
                        out.sendString("unpack error " + unpackError.getMessage());
                        if (forClient) {
                                for (final ReceiveCommand cmd : commands) {
                                        out.sendString("ng " + cmd.getRefName()
                                                        + " n/a (unpacker error)");
                                }
                        }
                        return;
                }

                if (forClient)
                        out.sendString("unpack ok");
                for (final ReceiveCommand cmd : commands) {
                        if (cmd.getResult() == Result.OK) {
                                if (forClient)
                                        out.sendString("ok " + cmd.getRefName());
                                continue;
                        }

                        final StringBuilder r = new StringBuilder();
                        r.append("ng ");
                        r.append(cmd.getRefName());
                        r.append(" ");

                        switch (cmd.getResult()) {
                        case NOT_ATTEMPTED:
                                r.append("server bug; ref not processed");
                                break;

                        case REJECTED_NOCREATE:
                                r.append("creation prohibited");
                                break;

                        case REJECTED_NODELETE:
                                r.append("deletion prohibited");
                                break;

                        case REJECTED_NONFASTFORWARD:
                                r.append("non-fast forward");
                                break;

                        case REJECTED_CURRENT_BRANCH:
                                r.append("branch is currently checked out");
                                break;

                        case REJECTED_MISSING_OBJECT:
                                if (cmd.getMessage() == null)
                                        r.append("missing object(s)");
                                else if (cmd.getMessage().length() == 2 * Constants.OBJECT_ID_LENGTH)
                                        r.append("object " + cmd.getMessage() + " missing");
                                else
                                        r.append(cmd.getMessage());
                                break;

                        case REJECTED_OTHER_REASON:
                                if (cmd.getMessage() == null)
                                        r.append("unspecified reason");
                                else
                                        r.append(cmd.getMessage());
                                break;

                        case LOCK_FAILURE:
                                r.append("failed to lock");
                                break;

                        case OK:
                                // We shouldn't have reached this case (see 'ok' case above).
                                continue;
                        }
                        out.sendString(r.toString());
                }
        }

        static abstract class Reporter {
                abstract void sendString(String s) throws IOException;
        }
}