org.eclipse.jgit/src/org/eclipse/jgit/transport/PushProcess.java - jgit - Git at Google

 /*
  * Copyright (C) 2008, 2022 Marek Zawirski <marek.zawirski@gmail.com> and others
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Distribution License v. 1.0 which is available at
  * https://www.eclipse.org/org/documents/edl-v10.php.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */

 package org.eclipse.jgit.transport;

 import java.io.IOException;
 import java.io.OutputStream;
 import java.text.MessageFormat;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;

 import org.eclipse.jgit.api.errors.AbortedByHookException;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.errors.NotSupportedException;
 import org.eclipse.jgit.errors.TransportException;
 import org.eclipse.jgit.hooks.PrePushHook;
 import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ProgressMonitor;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.revwalk.RevObject;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.transport.RemoteRefUpdate.Status;

 /**
  * Class performing push operation on remote repository.
  *
  * @see Transport#push(ProgressMonitor, Collection, OutputStream)
  */
 class PushProcess {
 	/** Task name for {@link ProgressMonitor} used during opening connection. */
 	static final String PROGRESS_OPENING_CONNECTION = JGitText.get().openingConnection;

 	/** Transport used to perform this operation. */
 	private final Transport transport;

 	/** Push operation connection created to perform this operation */
 	private PushConnection connection;

 	/** Refs to update on remote side. */
 	private final Map<String, RemoteRefUpdate> toPush;

 	/** Revision walker for checking some updates properties. */
 	private final RevWalk walker;

 	/** an outputstream to write messages to */
 	private final OutputStream out;

 	/** A list of option strings associated with this push */
 	private List<String> pushOptions;

 	private final PrePushHook prePush;

 	/**
 	 * Create process for specified transport and refs updates specification.
 	 *
 	 * @param transport
 	 *            transport between remote and local repository, used to create
 	 *            connection.
 	 * @param toPush
 	 *            specification of refs updates (and local tracking branches).
 	 * @param prePush
 	 *            {@link PrePushHook} to run after the remote advertisement has
 	 *            been gotten
 	 * @throws TransportException
 	 *             if a protocol error occurred during push/fetch
 	 */
 	PushProcess(Transport transport, Collection<RemoteRefUpdate> toPush,
 			PrePushHook prePush) throws TransportException {
 		this(transport, toPush, prePush, null);
 	}

 	/**
 	 * Create process for specified transport and refs updates specification.
 	 *
 	 * @param transport
 	 *            transport between remote and local repository, used to create
 	 *            connection.
 	 * @param toPush
 	 *            specification of refs updates (and local tracking branches).
 	 * @param prePush
 	 *            {@link PrePushHook} to run after the remote advertisement has
 	 *            been gotten
 	 * @param out
 	 *            OutputStream to write messages to
 	 * @throws TransportException
 	 *             if a protocol error occurred during push/fetch
 	 */
 	PushProcess(Transport transport, Collection<RemoteRefUpdate> toPush,
 			PrePushHook prePush, OutputStream out) throws TransportException {
 		this.walker = new RevWalk(transport.local);
 		this.transport = transport;
 		this.toPush = new LinkedHashMap<>();
 		this.prePush = prePush;
 		this.out = out;
 		this.pushOptions = transport.getPushOptions();
 		for (RemoteRefUpdate rru : toPush) {
 			if (this.toPush.put(rru.getRemoteName(), rru) != null)
 				throw new TransportException(MessageFormat.format(
 						JGitText.get().duplicateRemoteRefUpdateIsIllegal, rru.getRemoteName()));
 		}
 	}

 	/**
 	 * Perform push operation between local and remote repository - set remote
 	 * refs appropriately, send needed objects and update local tracking refs.
 	 * <p>
 	 * When {@link Transport#isDryRun()} is true, result of this operation is
 	 * just estimation of real operation result, no real action is performed.
 	 *
 	 * @param monitor
 	 *            progress monitor used for feedback about operation.
 	 * @return result of push operation with complete status description.
 	 * @throws NotSupportedException
 	 *             when push operation is not supported by provided transport.
 	 * @throws TransportException
 	 *             when some error occurred during operation, like I/O, protocol
 	 *             error, or local database consistency error.
 	 */
 	PushResult execute(ProgressMonitor monitor)
 			throws NotSupportedException, TransportException {
 		try {
 			monitor.beginTask(PROGRESS_OPENING_CONNECTION,
 					ProgressMonitor.UNKNOWN);

 			final PushResult res = new PushResult();
 			connection = transport.openPush();
 			try {
 				res.setAdvertisedRefs(transport.getURI(), connection
 						.getRefsMap());
 				res.peerUserAgent = connection.getPeerUserAgent();
 				monitor.endTask();

 				Map<String, RemoteRefUpdate> expanded = expandMatching();
 				toPush.clear();
 				toPush.putAll(expanded);

 				res.setRemoteUpdates(toPush);
 				final Map<String, RemoteRefUpdate> preprocessed = prepareRemoteUpdates();
 				List<RemoteRefUpdate> willBeAttempted = preprocessed.values()
 						.stream().filter(u -> {
 							switch (u.getStatus()) {
 							case NON_EXISTING:
 							case REJECTED_NODELETE:
 							case REJECTED_NONFASTFORWARD:
 							case REJECTED_OTHER_REASON:
 							case REJECTED_REMOTE_CHANGED:
 							case UP_TO_DATE:
 								return false;
 							default:
 								return true;
 							}
 						}).collect(Collectors.toList());
 				if (!willBeAttempted.isEmpty()) {
 					if (prePush != null) {
 						try {
 							prePush.setRefs(willBeAttempted);
 							prePush.setDryRun(transport.isDryRun());
 							prePush.call();
 						} catch (AbortedByHookException | IOException e) {
 							throw new TransportException(e.getMessage(), e);
 						}
 					}
 				}
 				if (transport.isDryRun())
 					modifyUpdatesForDryRun();
 				else if (!preprocessed.isEmpty())
 					connection.push(monitor, preprocessed, out);
 			} finally {
 				connection.close();
 				res.addMessages(connection.getMessages());
 			}
 			if (!transport.isDryRun())
 				updateTrackingRefs();
 			for (RemoteRefUpdate rru : toPush.values()) {
 				final TrackingRefUpdate tru = rru.getTrackingRefUpdate();
 				if (tru != null)
 					res.add(tru);
 			}
 			return res;
 		} finally {
 			walker.close();
 		}
 	}

 	private Map<String, RemoteRefUpdate> prepareRemoteUpdates()
 			throws TransportException {
 		boolean atomic = transport.isPushAtomic();
 		final Map<String, RemoteRefUpdate> result = new LinkedHashMap<>();
 		for (RemoteRefUpdate rru : toPush.values()) {
 			final Ref advertisedRef = connection.getRef(rru.getRemoteName());
 			ObjectId advertisedOld = null;
 			if (advertisedRef != null) {
 				advertisedOld = advertisedRef.getObjectId();
 			}
 			if (advertisedOld == null) {
 				advertisedOld = ObjectId.zeroId();
 			}

 			if (rru.getNewObjectId().equals(advertisedOld)) {
 				if (rru.isDelete()) {
 					// ref does exist neither locally nor remotely
 					rru.setStatus(Status.NON_EXISTING);
 				} else {
 					// same object - nothing to do
 					rru.setStatus(Status.UP_TO_DATE);
 				}
 				continue;
 			}

 			// caller has explicitly specified expected old object id, while it
 			// has been changed in the mean time - reject
 			if (rru.isExpectingOldObjectId()
 					&& !rru.getExpectedOldObjectId().equals(advertisedOld)) {
 				rru.setStatus(Status.REJECTED_REMOTE_CHANGED);
 				if (atomic) {
 					return rejectAll();
 				}
 				continue;
 			}
 			if (!rru.isExpectingOldObjectId()) {
 				rru.setExpectedOldObjectId(advertisedOld);
 			}

 			// create ref (hasn't existed on remote side) and delete ref
 			// are always fast-forward commands, feasible at this level
 			if (advertisedOld.equals(ObjectId.zeroId()) || rru.isDelete()) {
 				rru.setFastForward(true);
 				result.put(rru.getRemoteName(), rru);
 				continue;
 			}

 			boolean fastForward = isFastForward(advertisedOld,
 					rru.getNewObjectId());
 			rru.setFastForward(fastForward);
 			if (!fastForward && !rru.isForceUpdate()) {
 				rru.setStatus(Status.REJECTED_NONFASTFORWARD);
 				if (atomic) {
 					return rejectAll();
 				}
 			} else {
 				result.put(rru.getRemoteName(), rru);
 			}
 		}
 		return result;
 	}

 	/**
 	 * Determines whether an update from {@code oldOid} to {@code newOid} is a
 	 * fast-forward update:
 	 * <ul>
 	 * <li>both old and new must be commits, AND</li>
 	 * <li>both of them must be known to us and exist in the repository,
 	 * AND</li>
 	 * <li>the old commit must be an ancestor of the new commit.</li>
 	 * </ul>
 	 *
 	 * @param oldOid
 	 *            {@link ObjectId} of the old commit
 	 * @param newOid
 	 *            {@link ObjectId} of the new commit
 	 * @return {@code true} if the update fast-forwards, {@code false} otherwise
 	 * @throws TransportException
 	 *             if a protocol error occurred during push/fetch
 	 */
 	private boolean isFastForward(ObjectId oldOid, ObjectId newOid)
 			throws TransportException {
 		try {
 			RevObject oldRev = walker.parseAny(oldOid);
 			RevObject newRev = walker.parseAny(newOid);
 			if (!(oldRev instanceof RevCommit) || !(newRev instanceof RevCommit)
 					|| !walker.isMergedInto((RevCommit) oldRev,
 							(RevCommit) newRev)) {
 				return false;
 			}
 		} catch (MissingObjectException x) {
 			return false;
 		} catch (Exception x) {
 			throw new TransportException(transport.getURI(),
 					MessageFormat.format(JGitText
 							.get().readingObjectsFromLocalRepositoryFailed,
 							x.getMessage()),
 					x);
 		}
 		return true;
 	}

 	/**
 	 * Expands all placeholder {@link RemoteRefUpdate}s for "matching"
 	 * {@link RefSpec}s ":" in {@link #toPush} and returns the resulting map in
 	 * which the placeholders have been replaced by their expansion.
 	 *
 	 * @return a new map of {@link RemoteRefUpdate}s keyed by remote name
 	 * @throws TransportException
 	 *             if the expansion results in duplicate updates
 	 */
 	private Map<String, RemoteRefUpdate> expandMatching()
 			throws TransportException {
 		Map<String, RemoteRefUpdate> result = new LinkedHashMap<>();
 		boolean hadMatch = false;
 		for (RemoteRefUpdate update : toPush.values()) {
 			if (update.isMatching()) {
 				if (hadMatch) {
 					throw new TransportException(MessageFormat.format(
 							JGitText.get().duplicateRemoteRefUpdateIsIllegal,
 							":")); //$NON-NLS-1$
 				}
 				expandMatching(result, update);
 				hadMatch = true;
 			} else if (result.put(update.getRemoteName(), update) != null) {
 				throw new TransportException(MessageFormat.format(
 						JGitText.get().duplicateRemoteRefUpdateIsIllegal,
 						update.getRemoteName()));
 			}
 		}
 		return result;
 	}

 	/**
 	 * Expands the placeholder {@link RemoteRefUpdate} {@code match} for a
 	 * "matching" {@link RefSpec} ":" or "+:" and puts the expansion into the
 	 * given map {@code updates}.
 	 *
 	 * @param updates
 	 *            map to put the expansion in
 	 * @param match
 	 *            the placeholder {@link RemoteRefUpdate} to expand
 	 *
 	 * @throws TransportException
 	 *             if the expansion results in duplicate updates, or the local
 	 *             branches cannot be determined
 	 */
 	private void expandMatching(Map<String, RemoteRefUpdate> updates,
 			RemoteRefUpdate match) throws TransportException {
 		try {
 			Map<String, Ref> advertisement = connection.getRefsMap();
 			Collection<RefSpec> fetchSpecs = match.getFetchSpecs();
 			boolean forceUpdate = match.isForceUpdate();
 			for (Ref local : transport.local.getRefDatabase()
 					.getRefsByPrefix(Constants.R_HEADS)) {
 				if (local.isSymbolic()) {
 					continue;
 				}
 				String name = local.getName();
 				Ref advertised = advertisement.get(name);
 				if (advertised == null || advertised.isSymbolic()) {
 					continue;
 				}
 				ObjectId oldOid = advertised.getObjectId();
 				if (oldOid == null || ObjectId.zeroId().equals(oldOid)) {
 					continue;
 				}
 				ObjectId newOid = local.getObjectId();
 				if (newOid == null || ObjectId.zeroId().equals(newOid)) {
 					continue;
 				}

 				RemoteRefUpdate rru = new RemoteRefUpdate(transport.local, name,
 						newOid, name, forceUpdate,
 						Transport.findTrackingRefName(name, fetchSpecs),
 						oldOid);
 				if (updates.put(rru.getRemoteName(), rru) != null) {
 					throw new TransportException(MessageFormat.format(
 							JGitText.get().duplicateRemoteRefUpdateIsIllegal,
 							rru.getRemoteName()));
 				}
 			}
 		} catch (IOException x) {
 			throw new TransportException(transport.getURI(),
 					MessageFormat.format(JGitText
 							.get().readingObjectsFromLocalRepositoryFailed,
 							x.getMessage()),
 					x);
 		}
 	}

 	private Map<String, RemoteRefUpdate> rejectAll() {
 		for (RemoteRefUpdate rru : toPush.values()) {
 			if (rru.getStatus() == Status.NOT_ATTEMPTED) {
 				rru.setStatus(RemoteRefUpdate.Status.REJECTED_OTHER_REASON);
 				rru.setMessage(JGitText.get().transactionAborted);
 			}
 		}
 		return Collections.emptyMap();
 	}

 	private void modifyUpdatesForDryRun() {
 		for (RemoteRefUpdate rru : toPush.values())
 			if (rru.getStatus() == Status.NOT_ATTEMPTED)
 				rru.setStatus(Status.OK);
 	}

 	private void updateTrackingRefs() {
 		for (RemoteRefUpdate rru : toPush.values()) {
 			final Status status = rru.getStatus();
 			if (rru.hasTrackingRefUpdate()
 					&& (status == Status.UP_TO_DATE || status == Status.OK)) {
 				// update local tracking branch only when there is a chance that
 				// it has changed; this is possible for:
 				// -updated (OK) status,
 				// -up to date (UP_TO_DATE) status
 				try {
 					rru.updateTrackingRef(walker);
 				} catch (IOException e) {
 					// ignore as RefUpdate has stored I/O error status
 				}
 			}
 		}
 	}

 	/**
 	 * Gets the list of option strings associated with this push.
 	 *
 	 * @return pushOptions
 	 * @since 4.5
 	 */
 	public List<String> getPushOptions() {
 		return pushOptions;
 	}
 }
	/*
	* Copyright (C) 2008, 2022 Marek Zawirski <marek.zawirski@gmail.com> and others
	*
	* This program and the accompanying materials are made available under the
	* terms of the Eclipse Distribution License v. 1.0 which is available at
	* https://www.eclipse.org/org/documents/edl-v10.php.
	*
	* SPDX-License-Identifier: BSD-3-Clause
	*/

	package org.eclipse.jgit.transport;

	import java.io.IOException;
	import java.io.OutputStream;
	import java.text.MessageFormat;
	import java.util.Collection;
	import java.util.Collections;
	import java.util.LinkedHashMap;
	import java.util.List;
	import java.util.Map;
	import java.util.stream.Collectors;

	import org.eclipse.jgit.api.errors.AbortedByHookException;
	import org.eclipse.jgit.errors.MissingObjectException;
	import org.eclipse.jgit.errors.NotSupportedException;
	import org.eclipse.jgit.errors.TransportException;
	import org.eclipse.jgit.hooks.PrePushHook;
	import org.eclipse.jgit.internal.JGitText;
	import org.eclipse.jgit.lib.Constants;
	import org.eclipse.jgit.lib.ObjectId;
	import org.eclipse.jgit.lib.ProgressMonitor;
	import org.eclipse.jgit.lib.Ref;
	import org.eclipse.jgit.revwalk.RevCommit;
	import org.eclipse.jgit.revwalk.RevObject;
	import org.eclipse.jgit.revwalk.RevWalk;
	import org.eclipse.jgit.transport.RemoteRefUpdate.Status;

	/**
	* Class performing push operation on remote repository.
	*
	* @see Transport#push(ProgressMonitor, Collection, OutputStream)
	*/
	class PushProcess {
	/** Task name for {@link ProgressMonitor} used during opening connection. */
	static final String PROGRESS_OPENING_CONNECTION = JGitText.get().openingConnection;

	/** Transport used to perform this operation. */
	private final Transport transport;

	/** Push operation connection created to perform this operation */
	private PushConnection connection;

	/** Refs to update on remote side. */
	private final Map<String, RemoteRefUpdate> toPush;

	/** Revision walker for checking some updates properties. */
	private final RevWalk walker;

	/** an outputstream to write messages to */
	private final OutputStream out;

	/** A list of option strings associated with this push */
	private List<String> pushOptions;

	private final PrePushHook prePush;

	/**
	* Create process for specified transport and refs updates specification.
	*
	* @param transport
	* transport between remote and local repository, used to create
	* connection.
	* @param toPush
	* specification of refs updates (and local tracking branches).
	* @param prePush
	* {@link PrePushHook} to run after the remote advertisement has
	* been gotten
	* @throws TransportException
	* if a protocol error occurred during push/fetch
	*/
	PushProcess(Transport transport, Collection<RemoteRefUpdate> toPush,
	PrePushHook prePush) throws TransportException {
	this(transport, toPush, prePush, null);
	}

	/**
	* Create process for specified transport and refs updates specification.
	*
	* @param transport
	* transport between remote and local repository, used to create
	* connection.
	* @param toPush
	* specification of refs updates (and local tracking branches).
	* @param prePush
	* {@link PrePushHook} to run after the remote advertisement has
	* been gotten
	* @param out
	* OutputStream to write messages to
	* @throws TransportException
	* if a protocol error occurred during push/fetch
	*/
	PushProcess(Transport transport, Collection<RemoteRefUpdate> toPush,
	PrePushHook prePush, OutputStream out) throws TransportException {
	this.walker = new RevWalk(transport.local);
	this.transport = transport;
	this.toPush = new LinkedHashMap<>();
	this.prePush = prePush;
	this.out = out;
	this.pushOptions = transport.getPushOptions();
	for (RemoteRefUpdate rru : toPush) {
	if (this.toPush.put(rru.getRemoteName(), rru) != null)
	throw new TransportException(MessageFormat.format(
	JGitText.get().duplicateRemoteRefUpdateIsIllegal, rru.getRemoteName()));
	}
	}

	/**
	* Perform push operation between local and remote repository - set remote
	* refs appropriately, send needed objects and update local tracking refs.
	* <p>
	* When {@link Transport#isDryRun()} is true, result of this operation is
	* just estimation of real operation result, no real action is performed.
	*
	* @param monitor
	* progress monitor used for feedback about operation.
	* @return result of push operation with complete status description.
	* @throws NotSupportedException
	* when push operation is not supported by provided transport.
	* @throws TransportException
	* when some error occurred during operation, like I/O, protocol
	* error, or local database consistency error.
	*/
	PushResult execute(ProgressMonitor monitor)
	throws NotSupportedException, TransportException {
	try {
	monitor.beginTask(PROGRESS_OPENING_CONNECTION,
	ProgressMonitor.UNKNOWN);

	final PushResult res = new PushResult();
	connection = transport.openPush();
	try {
	res.setAdvertisedRefs(transport.getURI(), connection
	.getRefsMap());
	res.peerUserAgent = connection.getPeerUserAgent();
	monitor.endTask();

	Map<String, RemoteRefUpdate> expanded = expandMatching();
	toPush.clear();
	toPush.putAll(expanded);

	res.setRemoteUpdates(toPush);
	final Map<String, RemoteRefUpdate> preprocessed = prepareRemoteUpdates();
	List<RemoteRefUpdate> willBeAttempted = preprocessed.values()
	.stream().filter(u -> {
	switch (u.getStatus()) {
	case NON_EXISTING:
	case REJECTED_NODELETE:
	case REJECTED_NONFASTFORWARD:
	case REJECTED_OTHER_REASON:
	case REJECTED_REMOTE_CHANGED:
	case UP_TO_DATE:
	return false;
	default:
	return true;
	}
	}).collect(Collectors.toList());
	if (!willBeAttempted.isEmpty()) {
	if (prePush != null) {
	try {
	prePush.setRefs(willBeAttempted);
	prePush.setDryRun(transport.isDryRun());
	prePush.call();
	} catch (AbortedByHookException \| IOException e) {
	throw new TransportException(e.getMessage(), e);
	}
	}
	}
	if (transport.isDryRun())
	modifyUpdatesForDryRun();
	else if (!preprocessed.isEmpty())
	connection.push(monitor, preprocessed, out);
	} finally {
	connection.close();
	res.addMessages(connection.getMessages());
	}
	if (!transport.isDryRun())
	updateTrackingRefs();
	for (RemoteRefUpdate rru : toPush.values()) {
	final TrackingRefUpdate tru = rru.getTrackingRefUpdate();
	if (tru != null)
	res.add(tru);
	}
	return res;
	} finally {
	walker.close();
	}
	}

	private Map<String, RemoteRefUpdate> prepareRemoteUpdates()
	throws TransportException {
	boolean atomic = transport.isPushAtomic();
	final Map<String, RemoteRefUpdate> result = new LinkedHashMap<>();
	for (RemoteRefUpdate rru : toPush.values()) {
	final Ref advertisedRef = connection.getRef(rru.getRemoteName());
	ObjectId advertisedOld = null;
	if (advertisedRef != null) {
	advertisedOld = advertisedRef.getObjectId();
	}
	if (advertisedOld == null) {
	advertisedOld = ObjectId.zeroId();
	}

	if (rru.getNewObjectId().equals(advertisedOld)) {
	if (rru.isDelete()) {
	// ref does exist neither locally nor remotely
	rru.setStatus(Status.NON_EXISTING);
	} else {
	// same object - nothing to do
	rru.setStatus(Status.UP_TO_DATE);
	}
	continue;
	}

	// caller has explicitly specified expected old object id, while it
	// has been changed in the mean time - reject
	if (rru.isExpectingOldObjectId()
	&& !rru.getExpectedOldObjectId().equals(advertisedOld)) {
	rru.setStatus(Status.REJECTED_REMOTE_CHANGED);
	if (atomic) {
	return rejectAll();
	}
	continue;
	}
	if (!rru.isExpectingOldObjectId()) {
	rru.setExpectedOldObjectId(advertisedOld);
	}

	// create ref (hasn't existed on remote side) and delete ref
	// are always fast-forward commands, feasible at this level
	if (advertisedOld.equals(ObjectId.zeroId()) \|\| rru.isDelete()) {
	rru.setFastForward(true);
	result.put(rru.getRemoteName(), rru);
	continue;
	}

	boolean fastForward = isFastForward(advertisedOld,
	rru.getNewObjectId());
	rru.setFastForward(fastForward);
	if (!fastForward && !rru.isForceUpdate()) {
	rru.setStatus(Status.REJECTED_NONFASTFORWARD);
	if (atomic) {
	return rejectAll();
	}
	} else {
	result.put(rru.getRemoteName(), rru);
	}
	}
	return result;
	}

	/**
	* Determines whether an update from {@code oldOid} to {@code newOid} is a
	* fast-forward update:
	* <ul>
	* <li>both old and new must be commits, AND</li>
	* <li>both of them must be known to us and exist in the repository,
	* AND</li>
	* <li>the old commit must be an ancestor of the new commit.</li>
	* </ul>
	*
	* @param oldOid
	* {@link ObjectId} of the old commit
	* @param newOid
	* {@link ObjectId} of the new commit
	* @return {@code true} if the update fast-forwards, {@code false} otherwise
	* @throws TransportException
	* if a protocol error occurred during push/fetch
	*/
	private boolean isFastForward(ObjectId oldOid, ObjectId newOid)
	throws TransportException {
	try {
	RevObject oldRev = walker.parseAny(oldOid);
	RevObject newRev = walker.parseAny(newOid);
	if (!(oldRev instanceof RevCommit) \|\| !(newRev instanceof RevCommit)
	\|\| !walker.isMergedInto((RevCommit) oldRev,
	(RevCommit) newRev)) {
	return false;
	}
	} catch (MissingObjectException x) {
	return false;
	} catch (Exception x) {
	throw new TransportException(transport.getURI(),
	MessageFormat.format(JGitText
	.get().readingObjectsFromLocalRepositoryFailed,
	x.getMessage()),
	x);
	}
	return true;
	}

	/**
	* Expands all placeholder {@link RemoteRefUpdate}s for "matching"
	* {@link RefSpec}s ":" in {@link #toPush} and returns the resulting map in
	* which the placeholders have been replaced by their expansion.
	*
	* @return a new map of {@link RemoteRefUpdate}s keyed by remote name
	* @throws TransportException
	* if the expansion results in duplicate updates
	*/
	private Map<String, RemoteRefUpdate> expandMatching()
	throws TransportException {
	Map<String, RemoteRefUpdate> result = new LinkedHashMap<>();
	boolean hadMatch = false;
	for (RemoteRefUpdate update : toPush.values()) {
	if (update.isMatching()) {
	if (hadMatch) {
	throw new TransportException(MessageFormat.format(
	JGitText.get().duplicateRemoteRefUpdateIsIllegal,
	":")); //$NON-NLS-1$
	}
	expandMatching(result, update);
	hadMatch = true;
	} else if (result.put(update.getRemoteName(), update) != null) {
	throw new TransportException(MessageFormat.format(
	JGitText.get().duplicateRemoteRefUpdateIsIllegal,
	update.getRemoteName()));
	}
	}
	return result;
	}

	/**
	* Expands the placeholder {@link RemoteRefUpdate} {@code match} for a
	* "matching" {@link RefSpec} ":" or "+:" and puts the expansion into the
	* given map {@code updates}.
	*
	* @param updates
	* map to put the expansion in
	* @param match
	* the placeholder {@link RemoteRefUpdate} to expand
	*
	* @throws TransportException
	* if the expansion results in duplicate updates, or the local
	* branches cannot be determined
	*/
	private void expandMatching(Map<String, RemoteRefUpdate> updates,
	RemoteRefUpdate match) throws TransportException {
	try {
	Map<String, Ref> advertisement = connection.getRefsMap();
	Collection<RefSpec> fetchSpecs = match.getFetchSpecs();
	boolean forceUpdate = match.isForceUpdate();
	for (Ref local : transport.local.getRefDatabase()
	.getRefsByPrefix(Constants.R_HEADS)) {
	if (local.isSymbolic()) {
	continue;
	}
	String name = local.getName();
	Ref advertised = advertisement.get(name);
	if (advertised == null \|\| advertised.isSymbolic()) {
	continue;
	}
	ObjectId oldOid = advertised.getObjectId();
	if (oldOid == null \|\| ObjectId.zeroId().equals(oldOid)) {
	continue;
	}
	ObjectId newOid = local.getObjectId();
	if (newOid == null \|\| ObjectId.zeroId().equals(newOid)) {
	continue;
	}

	RemoteRefUpdate rru = new RemoteRefUpdate(transport.local, name,
	newOid, name, forceUpdate,
	Transport.findTrackingRefName(name, fetchSpecs),
	oldOid);
	if (updates.put(rru.getRemoteName(), rru) != null) {
	throw new TransportException(MessageFormat.format(
	JGitText.get().duplicateRemoteRefUpdateIsIllegal,
	rru.getRemoteName()));
	}
	}
	} catch (IOException x) {
	throw new TransportException(transport.getURI(),
	MessageFormat.format(JGitText
	.get().readingObjectsFromLocalRepositoryFailed,
	x.getMessage()),
	x);
	}
	}

	private Map<String, RemoteRefUpdate> rejectAll() {
	for (RemoteRefUpdate rru : toPush.values()) {
	if (rru.getStatus() == Status.NOT_ATTEMPTED) {
	rru.setStatus(RemoteRefUpdate.Status.REJECTED_OTHER_REASON);
	rru.setMessage(JGitText.get().transactionAborted);
	}
	}
	return Collections.emptyMap();
	}

	private void modifyUpdatesForDryRun() {
	for (RemoteRefUpdate rru : toPush.values())
	if (rru.getStatus() == Status.NOT_ATTEMPTED)
	rru.setStatus(Status.OK);
	}

	private void updateTrackingRefs() {
	for (RemoteRefUpdate rru : toPush.values()) {
	final Status status = rru.getStatus();
	if (rru.hasTrackingRefUpdate()
	&& (status == Status.UP_TO_DATE \|\| status == Status.OK)) {
	// update local tracking branch only when there is a chance that
	// it has changed; this is possible for:
	// -updated (OK) status,
	// -up to date (UP_TO_DATE) status
	try {
	rru.updateTrackingRef(walker);
	} catch (IOException e) {
	// ignore as RefUpdate has stored I/O error status
	}
	}
	}
	}

	/**
	* Gets the list of option strings associated with this push.
	*
	* @return pushOptions
	* @since 4.5
	*/
	public List<String> getPushOptions() {
	return pushOptions;
	}
	}