org.eclipse.jgit/src/org/eclipse/jgit/lib/BatchRefUpdate.java - jgit - Git at Google

 /*
  * Copyright (C) 2008-2012, Google Inc.
  * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org> 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.lib;

 import static org.eclipse.jgit.transport.ReceiveCommand.Result.NOT_ATTEMPTED;
 import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_OTHER_REASON;

 import java.io.IOException;
 import java.text.MessageFormat;
 import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
 import java.util.concurrent.TimeoutException;

 import org.eclipse.jgit.annotations.Nullable;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.transport.PushCertificate;
 import org.eclipse.jgit.transport.ReceiveCommand;
 import org.eclipse.jgit.util.time.ProposedTimestamp;

 /**
  * Batch of reference updates to be applied to a repository.
  * <p>
  * The batch update is primarily useful in the transport code, where a client or
  * server is making changes to more than one reference at a time.
  */
 public class BatchRefUpdate {
 	/**
 	 * Maximum delay the calling thread will tolerate while waiting for a
 	 * {@code MonotonicClock} to resolve associated {@link ProposedTimestamp}s.
 	 * <p>
 	 * A default of 5 seconds was chosen by guessing. A common assumption is
 	 * clock skew between machines on the same LAN using an NTP server also on
 	 * the same LAN should be under 5 seconds. 5 seconds is also not that long
 	 * for a large `git push` operation to complete.
 	 *
 	 * @since 4.9
 	 */
 	protected static final Duration MAX_WAIT = Duration.ofSeconds(5);

 	private final RefDatabase refdb;

 	/** Commands to apply during this batch. */
 	private final List<ReceiveCommand> commands;

 	/** Does the caller permit a forced update on a reference? */
 	private boolean allowNonFastForwards;

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

 	/** Message the caller wants included in the reflog. */
 	private String refLogMessage;

 	/** Should the result value be appended to {@link #refLogMessage}. */
 	private boolean refLogIncludeResult;

 	/**
 	 * Should reflogs be written even if the configured default for this ref is
 	 * not to write it.
 	 */
 	private boolean forceRefLog;

 	/** Push certificate associated with this update. */
 	private PushCertificate pushCert;

 	/** Whether updates should be atomic. */
 	private boolean atomic;

 	/** Push options associated with this update. */
 	private List<String> pushOptions;

 	/** Associated timestamps that should be blocked on before update. */
 	private List<ProposedTimestamp> timestamps;

 	/**
 	 * Initialize a new batch update.
 	 *
 	 * @param refdb
 	 *            the reference database of the repository to be updated.
 	 */
 	protected BatchRefUpdate(RefDatabase refdb) {
 		this.refdb = refdb;
 		this.commands = new ArrayList<>();
 		this.atomic = refdb.performsAtomicTransactions();
 	}

 	/**
 	 * Whether the batch update will permit a non-fast-forward update to an
 	 * existing reference.
 	 *
 	 * @return true if the batch update will permit a non-fast-forward update to
 	 *         an existing reference.
 	 */
 	public boolean isAllowNonFastForwards() {
 		return allowNonFastForwards;
 	}

 	/**
 	 * Set if this update wants to permit a forced update.
 	 *
 	 * @param allow
 	 *            true if this update batch should ignore merge tests.
 	 * @return {@code this}.
 	 */
 	public BatchRefUpdate setAllowNonFastForwards(boolean allow) {
 		allowNonFastForwards = allow;
 		return this;
 	}

 	/**
 	 * Get identity of the user making the change in the reflog.
 	 *
 	 * @return identity of the user making the change in the reflog.
 	 */
 	public PersonIdent getRefLogIdent() {
 		return refLogIdent;
 	}

 	/**
 	 * Set the identity of the user appearing in the reflog.
 	 * <p>
 	 * The timestamp portion of the identity is ignored. A new identity with the
 	 * current timestamp will be created automatically when the update occurs
 	 * and the log record is written.
 	 *
 	 * @param pi
 	 *            identity of the user. If null the identity will be
 	 *            automatically determined based on the repository
 	 *            configuration.
 	 * @return {@code this}.
 	 */
 	public BatchRefUpdate setRefLogIdent(PersonIdent pi) {
 		refLogIdent = pi;
 		return this;
 	}

 	/**
 	 * Get the message to include in the reflog.
 	 *
 	 * @return message the caller wants to include in the reflog; null if the
 	 *         update should not be logged.
 	 */
 	@Nullable
 	public String getRefLogMessage() {
 		return refLogMessage;
 	}

 	/**
 	 * Check whether the reflog message should include the result of the update,
 	 * such as fast-forward or force-update.
 	 * <p>
 	 * Describes the default for commands in this batch that do not override it
 	 * with
 	 * {@link org.eclipse.jgit.transport.ReceiveCommand#setRefLogMessage(String, boolean)}.
 	 *
 	 * @return true if the message should include the result.
 	 */
 	public boolean isRefLogIncludingResult() {
 		return refLogIncludeResult;
 	}

 	/**
 	 * Set the message to include in the reflog.
 	 * <p>
 	 * Repository implementations may limit which reflogs are written by
 	 * default, based on the project configuration. If a repo is not configured
 	 * to write logs for this ref by default, setting the message alone may have
 	 * no effect. To indicate that the repo should write logs for this update in
 	 * spite of configured defaults, use {@link #setForceRefLog(boolean)}.
 	 * <p>
 	 * Describes the default for commands in this batch that do not override it
 	 * with
 	 * {@link org.eclipse.jgit.transport.ReceiveCommand#setRefLogMessage(String, boolean)}.
 	 *
 	 * @param msg
 	 *            the message to describe this change. If null and appendStatus
 	 *            is false, the reflog will not be updated.
 	 * @param appendStatus
 	 *            true if the status of the ref change (fast-forward or
 	 *            forced-update) should be appended to the user supplied
 	 *            message.
 	 * @return {@code this}.
 	 */
 	public BatchRefUpdate setRefLogMessage(String msg, boolean appendStatus) {
 		if (msg == null && !appendStatus)
 			disableRefLog();
 		else if (msg == null && appendStatus) {
 			refLogMessage = ""; //$NON-NLS-1$
 			refLogIncludeResult = true;
 		} else {
 			refLogMessage = msg;
 			refLogIncludeResult = appendStatus;
 		}
 		return this;
 	}

 	/**
 	 * Don't record this update in the ref's associated reflog.
 	 * <p>
 	 * Equivalent to {@code setRefLogMessage(null, false)}.
 	 *
 	 * @return {@code this}.
 	 */
 	public BatchRefUpdate disableRefLog() {
 		refLogMessage = null;
 		refLogIncludeResult = false;
 		return this;
 	}

 	/**
 	 * Force writing a reflog for the updated ref.
 	 *
 	 * @param force whether to force.
 	 * @return {@code this}
 	 * @since 4.9
 	 */
 	public BatchRefUpdate setForceRefLog(boolean force) {
 		forceRefLog = force;
 		return this;
 	}

 	/**
 	 * Check whether log has been disabled by {@link #disableRefLog()}.
 	 *
 	 * @return true if disabled.
 	 */
 	public boolean isRefLogDisabled() {
 		return refLogMessage == null;
 	}

 	/**
 	 * Check whether the reflog should be written regardless of repo defaults.
 	 *
 	 * @return whether force writing is enabled.
 	 * @since 4.9
 	 */
 	protected boolean isForceRefLog() {
 		return forceRefLog;
 	}

 	/**
 	 * Request that all updates in this batch be performed atomically.
 	 * <p>
 	 * When atomic updates are used, either all commands apply successfully, or
 	 * none do. Commands that might have otherwise succeeded are rejected with
 	 * {@code REJECTED_OTHER_REASON}.
 	 * <p>
 	 * This method only works if the underlying ref database supports atomic
 	 * transactions, i.e.
 	 * {@link org.eclipse.jgit.lib.RefDatabase#performsAtomicTransactions()}
 	 * returns true. Calling this method with true if the underlying ref
 	 * database does not support atomic transactions will cause all commands to
 	 * fail with {@code
 	 * REJECTED_OTHER_REASON}.
 	 *
 	 * @param atomic
 	 *            whether updates should be atomic.
 	 * @return {@code this}
 	 * @since 4.4
 	 */
 	public BatchRefUpdate setAtomic(boolean atomic) {
 		this.atomic = atomic;
 		return this;
 	}

 	/**
 	 * Whether updates should be atomic.
 	 *
 	 * @return atomic whether updates should be atomic.
 	 * @since 4.4
 	 */
 	public boolean isAtomic() {
 		return atomic;
 	}

 	/**
 	 * Set a push certificate associated with this update.
 	 * <p>
 	 * This usually includes commands to update the refs in this batch, but is not
 	 * required to.
 	 *
 	 * @param cert
 	 *            push certificate, may be null.
 	 * @since 4.1
 	 */
 	public void setPushCertificate(PushCertificate cert) {
 		pushCert = cert;
 	}

 	/**
 	 * Set the push certificate associated with this update.
 	 * <p>
 	 * This usually includes commands to update the refs in this batch, but is not
 	 * required to.
 	 *
 	 * @return push certificate, may be null.
 	 * @since 4.1
 	 */
 	protected PushCertificate getPushCertificate() {
 		return pushCert;
 	}

 	/**
 	 * Get commands this update will process.
 	 *
 	 * @return commands this update will process.
 	 */
 	public List<ReceiveCommand> getCommands() {
 		return Collections.unmodifiableList(commands);
 	}

 	/**
 	 * Add a single command to this batch update.
 	 *
 	 * @param cmd
 	 *            the command to add, must not be null.
 	 * @return {@code this}.
 	 */
 	public BatchRefUpdate addCommand(ReceiveCommand cmd) {
 		commands.add(cmd);
 		return this;
 	}

 	/**
 	 * Add commands to this batch update.
 	 *
 	 * @param cmd
 	 *            the commands to add, must not be null.
 	 * @return {@code this}.
 	 */
 	public BatchRefUpdate addCommand(ReceiveCommand... cmd) {
 		return addCommand(Arrays.asList(cmd));
 	}

 	/**
 	 * Add commands to this batch update.
 	 *
 	 * @param cmd
 	 *            the commands to add, must not be null.
 	 * @return {@code this}.
 	 */
 	public BatchRefUpdate addCommand(Collection<ReceiveCommand> cmd) {
 		commands.addAll(cmd);
 		return this;
 	}

 	/**
 	 * Gets the list of option strings associated with this update.
 	 *
 	 * @return push options that were passed to {@link #execute}; prior to calling
 	 *         {@link #execute}, always returns null.
 	 * @since 4.5
 	 */
 	@Nullable
 	public List<String> getPushOptions() {
 		return pushOptions;
 	}

 	/**
 	 * Set push options associated with this update.
 	 * <p>
 	 * Implementations must call this at the top of {@link #execute(RevWalk,
 	 * ProgressMonitor, List)}.
 	 *
 	 * @param options options passed to {@code execute}.
 	 * @since 4.9
 	 */
 	protected void setPushOptions(List<String> options) {
 		pushOptions = options;
 	}

 	/**
 	 * Get list of timestamps the batch must wait for.
 	 *
 	 * @return list of timestamps the batch must wait for.
 	 * @since 4.6
 	 */
 	public List<ProposedTimestamp> getProposedTimestamps() {
 		if (timestamps != null) {
 			return Collections.unmodifiableList(timestamps);
 		}
 		return Collections.emptyList();
 	}

 	/**
 	 * Request the batch to wait for the affected timestamps to resolve.
 	 *
 	 * @param ts
 	 *            a {@link org.eclipse.jgit.util.time.ProposedTimestamp} object.
 	 * @return {@code this}.
 	 * @since 4.6
 	 */
 	public BatchRefUpdate addProposedTimestamp(ProposedTimestamp ts) {
 		if (timestamps == null) {
 			timestamps = new ArrayList<>(4);
 		}
 		timestamps.add(ts);
 		return this;
 	}

 	/**
 	 * Execute this batch update.
 	 * <p>
 	 * The default implementation of this method performs a sequential reference
 	 * update over each reference.
 	 * <p>
 	 * Implementations must respect the atomicity requirements of the underlying
 	 * database as described in {@link #setAtomic(boolean)} and
 	 * {@link org.eclipse.jgit.lib.RefDatabase#performsAtomicTransactions()}.
 	 *
 	 * @param walk
 	 *            a RevWalk to parse tags in case the storage system wants to
 	 *            store them pre-peeled, a common performance optimization.
 	 * @param monitor
 	 *            progress monitor to receive update status on.
 	 * @param options
 	 *            a list of option strings; set null to execute without
 	 * @throws java.io.IOException
 	 *             the database is unable to accept the update. Individual
 	 *             command status must be tested to determine if there is a
 	 *             partial failure, or a total failure.
 	 * @since 4.5
 	 */
 	public void execute(RevWalk walk, ProgressMonitor monitor,
 			List<String> options) throws IOException {

 		if (atomic && !refdb.performsAtomicTransactions()) {
 			for (ReceiveCommand c : commands) {
 				if (c.getResult() == NOT_ATTEMPTED) {
 					c.setResult(REJECTED_OTHER_REASON,
 							JGitText.get().atomicRefUpdatesNotSupported);
 				}
 			}
 			return;
 		}
 		if (!blockUntilTimestamps(MAX_WAIT)) {
 			return;
 		}

 		if (options != null) {
 			setPushOptions(options);
 		}

 		monitor.beginTask(JGitText.get().updatingReferences, commands.size());
 		List<ReceiveCommand> commands2 = new ArrayList<>(
 				commands.size());
 		// First delete refs. This may free the name space for some of the
 		// updates.
 		for (ReceiveCommand cmd : commands) {
 			try {
 				if (cmd.getResult() == NOT_ATTEMPTED) {
 					if (isMissing(walk, cmd.getOldId())
 							|| isMissing(walk, cmd.getNewId())) {
 						cmd.setResult(ReceiveCommand.Result.REJECTED_MISSING_OBJECT);
 						continue;
 					}
 					cmd.updateType(walk);
 					switch (cmd.getType()) {
 					case CREATE:
 						commands2.add(cmd);
 						break;
 					case UPDATE:
 					case UPDATE_NONFASTFORWARD:
 						commands2.add(cmd);
 						break;
 					case DELETE:
 						RefUpdate rud = newUpdate(cmd);
 						monitor.update(1);
 						cmd.setResult(rud.delete(walk));
 					}
 				}
 			} catch (IOException err) {
 				cmd.setResult(
 						REJECTED_OTHER_REASON,
 						MessageFormat.format(JGitText.get().lockError,
 								err.getMessage()));
 			}
 		}
 		if (!commands2.isEmpty()) {
 			// Perform updates that may require more room in the name space
 			for (ReceiveCommand cmd : commands2) {
 				try {
 					if (cmd.getResult() == NOT_ATTEMPTED) {
 						cmd.updateType(walk);
 						RefUpdate ru = newUpdate(cmd);
 						switch (cmd.getType()) {
 							case DELETE:
 								// Performed in the first phase
 								break;
 							case UPDATE:
 							case UPDATE_NONFASTFORWARD:
 								RefUpdate ruu = newUpdate(cmd);
 								cmd.setResult(ruu.update(walk));
 								break;
 							case CREATE:
 								cmd.setResult(ru.update(walk));
 								break;
 						}
 					}
 				} catch (IOException err) {
 					cmd.setResult(REJECTED_OTHER_REASON, MessageFormat.format(
 							JGitText.get().lockError, err.getMessage()));
 				} finally {
 					monitor.update(1);
 				}
 			}
 		}
 		monitor.endTask();
 	}

 	private static boolean isMissing(RevWalk walk, ObjectId id)
 			throws IOException {
 		if (id.equals(ObjectId.zeroId())) {
 			return false; // Explicit add or delete is not missing.
 		}
 		try {
 			walk.parseAny(id);
 			return false;
 		} catch (MissingObjectException e) {
 			return true;
 		}
 	}

 	/**
 	 * Wait for timestamps to be in the past, aborting commands on timeout.
 	 *
 	 * @param maxWait
 	 *            maximum amount of time to wait for timestamps to resolve.
 	 * @return true if timestamps were successfully waited for; false if
 	 *         commands were aborted.
 	 * @since 4.6
 	 */
 	protected boolean blockUntilTimestamps(Duration maxWait) {
 		if (timestamps == null) {
 			return true;
 		}
 		try {
 			ProposedTimestamp.blockUntil(timestamps, maxWait);
 			return true;
 		} catch (TimeoutException | InterruptedException e) {
 			String msg = JGitText.get().timeIsUncertain;
 			for (ReceiveCommand c : commands) {
 				if (c.getResult() == NOT_ATTEMPTED) {
 					c.setResult(REJECTED_OTHER_REASON, msg);
 				}
 			}
 			return false;
 		}
 	}

 	/**
 	 * Execute this batch update without option strings.
 	 *
 	 * @param walk
 	 *            a RevWalk to parse tags in case the storage system wants to
 	 *            store them pre-peeled, a common performance optimization.
 	 * @param monitor
 	 *            progress monitor to receive update status on.
 	 * @throws java.io.IOException
 	 *             the database is unable to accept the update. Individual
 	 *             command status must be tested to determine if there is a
 	 *             partial failure, or a total failure.
 	 */
 	public void execute(RevWalk walk, ProgressMonitor monitor)
 			throws IOException {
 		execute(walk, monitor, null);
 	}

 	/**
 	 * Get all path prefixes of a ref name.
 	 *
 	 * @param name
 	 *            ref name.
 	 * @return path prefixes of the ref name. For {@code refs/heads/foo}, returns
 	 *         {@code refs} and {@code refs/heads}.
 	 * @since 4.9
 	 */
 	protected static Collection<String> getPrefixes(String name) {
 		Collection<String> ret = new HashSet<>();
 		addPrefixesTo(name, ret);
 		return ret;
 	}

 	/**
 	 * Add prefixes of a ref name to an existing collection.
 	 *
 	 * @param name
 	 *            ref name.
 	 * @param out
 	 *            path prefixes of the ref name. For {@code refs/heads/foo},
 	 *            returns {@code refs} and {@code refs/heads}.
 	 * @since 4.9
 	 */
 	protected static void addPrefixesTo(String name, Collection<String> out) {
 		int p1 = name.indexOf('/');
 		while (p1 > 0) {
 			out.add(name.substring(0, p1));
 			p1 = name.indexOf('/', p1 + 1);
 		}
 	}

 	/**
 	 * Create a new RefUpdate copying the batch settings.
 	 *
 	 * @param cmd
 	 *            specific command the update should be created to copy.
 	 * @return a single reference update command.
 	 * @throws java.io.IOException
 	 *             the reference database cannot make a new update object for
 	 *             the given reference.
 	 */
 	protected RefUpdate newUpdate(ReceiveCommand cmd) throws IOException {
 		RefUpdate ru = refdb.newUpdate(cmd.getRefName(), false);
 		if (isRefLogDisabled(cmd)) {
 			ru.disableRefLog();
 		} else {
 			ru.setRefLogIdent(refLogIdent);
 			ru.setRefLogMessage(getRefLogMessage(cmd), isRefLogIncludingResult(cmd));
 			ru.setForceRefLog(isForceRefLog(cmd));
 		}
 		ru.setPushCertificate(pushCert);
 		switch (cmd.getType()) {
 		case DELETE:
 			if (!ObjectId.zeroId().equals(cmd.getOldId()))
 				ru.setExpectedOldObjectId(cmd.getOldId());
 			ru.setForceUpdate(true);
 			return ru;

 		case CREATE:
 		case UPDATE:
 		case UPDATE_NONFASTFORWARD:
 		default:
 			ru.setForceUpdate(isAllowNonFastForwards());
 			ru.setExpectedOldObjectId(cmd.getOldId());
 			ru.setNewObjectId(cmd.getNewId());
 			return ru;
 		}
 	}

 	/**
 	 * Check whether reflog is disabled for a command.
 	 *
 	 * @param cmd
 	 *            specific command.
 	 * @return whether the reflog is disabled, taking into account the state from
 	 *         this instance as well as overrides in the given command.
 	 * @since 4.9
 	 */
 	protected boolean isRefLogDisabled(ReceiveCommand cmd) {
 		return cmd.hasCustomRefLog() ? cmd.isRefLogDisabled() : isRefLogDisabled();
 	}

 	/**
 	 * Get reflog message for a command.
 	 *
 	 * @param cmd
 	 *            specific command.
 	 * @return reflog message, taking into account the state from this instance as
 	 *         well as overrides in the given command.
 	 * @since 4.9
 	 */
 	protected String getRefLogMessage(ReceiveCommand cmd) {
 		return cmd.hasCustomRefLog() ? cmd.getRefLogMessage() : getRefLogMessage();
 	}

 	/**
 	 * Check whether the reflog message for a command should include the result.
 	 *
 	 * @param cmd
 	 *            specific command.
 	 * @return whether the reflog message should show the result, taking into
 	 *         account the state from this instance as well as overrides in the
 	 *         given command.
 	 * @since 4.9
 	 */
 	protected boolean isRefLogIncludingResult(ReceiveCommand cmd) {
 		return cmd.hasCustomRefLog()
 				? cmd.isRefLogIncludingResult() : isRefLogIncludingResult();
 	}

 	/**
 	 * Check whether the reflog for a command should be written regardless of repo
 	 * defaults.
 	 *
 	 * @param cmd
 	 *            specific command.
 	 * @return whether force writing is enabled.
 	 * @since 4.9
 	 */
 	protected boolean isForceRefLog(ReceiveCommand cmd) {
 		Boolean isForceRefLog = cmd.isForceRefLog();
 		return isForceRefLog != null ? isForceRefLog.booleanValue()
 				: isForceRefLog();
 	}

 	/** {@inheritDoc} */
 	@Override
 	public String toString() {
 		StringBuilder r = new StringBuilder();
 		r.append(getClass().getSimpleName()).append('[');
 		if (commands.isEmpty())
 			return r.append(']').toString();

 		r.append('\n');
 		for (ReceiveCommand cmd : commands) {
 			r.append("  "); //$NON-NLS-1$
 			r.append(cmd);
 			r.append("  (").append(cmd.getResult()); //$NON-NLS-1$
 			if (cmd.getMessage() != null) {
 				r.append(": ").append(cmd.getMessage()); //$NON-NLS-1$
 			}
 			r.append(")\n"); //$NON-NLS-1$
 		}
 		return r.append(']').toString();
 	}
 }
	/*
	* Copyright (C) 2008-2012, Google Inc.
	* Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org> 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.lib;

	import static org.eclipse.jgit.transport.ReceiveCommand.Result.NOT_ATTEMPTED;
	import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_OTHER_REASON;

	import java.io.IOException;
	import java.text.MessageFormat;
	import java.time.Duration;
	import java.util.ArrayList;
	import java.util.Arrays;
	import java.util.Collection;
	import java.util.Collections;
	import java.util.HashSet;
	import java.util.List;
	import java.util.concurrent.TimeoutException;

	import org.eclipse.jgit.annotations.Nullable;
	import org.eclipse.jgit.errors.MissingObjectException;
	import org.eclipse.jgit.internal.JGitText;
	import org.eclipse.jgit.revwalk.RevWalk;
	import org.eclipse.jgit.transport.PushCertificate;
	import org.eclipse.jgit.transport.ReceiveCommand;
	import org.eclipse.jgit.util.time.ProposedTimestamp;

	/**
	* Batch of reference updates to be applied to a repository.
	* <p>
	* The batch update is primarily useful in the transport code, where a client or
	* server is making changes to more than one reference at a time.
	*/
	public class BatchRefUpdate {
	/**
	* Maximum delay the calling thread will tolerate while waiting for a
	* {@code MonotonicClock} to resolve associated {@link ProposedTimestamp}s.
	* <p>
	* A default of 5 seconds was chosen by guessing. A common assumption is
	* clock skew between machines on the same LAN using an NTP server also on
	* the same LAN should be under 5 seconds. 5 seconds is also not that long
	* for a large `git push` operation to complete.
	*
	* @since 4.9
	*/
	protected static final Duration MAX_WAIT = Duration.ofSeconds(5);

	private final RefDatabase refdb;

	/** Commands to apply during this batch. */
	private final List<ReceiveCommand> commands;

	/** Does the caller permit a forced update on a reference? */
	private boolean allowNonFastForwards;

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

	/** Message the caller wants included in the reflog. */
	private String refLogMessage;

	/** Should the result value be appended to {@link #refLogMessage}. */
	private boolean refLogIncludeResult;

	/**
	* Should reflogs be written even if the configured default for this ref is
	* not to write it.
	*/
	private boolean forceRefLog;

	/** Push certificate associated with this update. */
	private PushCertificate pushCert;

	/** Whether updates should be atomic. */
	private boolean atomic;

	/** Push options associated with this update. */
	private List<String> pushOptions;

	/** Associated timestamps that should be blocked on before update. */
	private List<ProposedTimestamp> timestamps;

	/**
	* Initialize a new batch update.
	*
	* @param refdb
	* the reference database of the repository to be updated.
	*/
	protected BatchRefUpdate(RefDatabase refdb) {
	this.refdb = refdb;
	this.commands = new ArrayList<>();
	this.atomic = refdb.performsAtomicTransactions();
	}

	/**
	* Whether the batch update will permit a non-fast-forward update to an
	* existing reference.
	*
	* @return true if the batch update will permit a non-fast-forward update to
	* an existing reference.
	*/
	public boolean isAllowNonFastForwards() {
	return allowNonFastForwards;
	}

	/**
	* Set if this update wants to permit a forced update.
	*
	* @param allow
	* true if this update batch should ignore merge tests.
	* @return {@code this}.
	*/
	public BatchRefUpdate setAllowNonFastForwards(boolean allow) {
	allowNonFastForwards = allow;
	return this;
	}

	/**
	* Get identity of the user making the change in the reflog.
	*
	* @return identity of the user making the change in the reflog.
	*/
	public PersonIdent getRefLogIdent() {
	return refLogIdent;
	}

	/**
	* Set the identity of the user appearing in the reflog.
	* <p>
	* The timestamp portion of the identity is ignored. A new identity with the
	* current timestamp will be created automatically when the update occurs
	* and the log record is written.
	*
	* @param pi
	* identity of the user. If null the identity will be
	* automatically determined based on the repository
	* configuration.
	* @return {@code this}.
	*/
	public BatchRefUpdate setRefLogIdent(PersonIdent pi) {
	refLogIdent = pi;
	return this;
	}

	/**
	* Get the message to include in the reflog.
	*
	* @return message the caller wants to include in the reflog; null if the
	* update should not be logged.
	*/
	@Nullable
	public String getRefLogMessage() {
	return refLogMessage;
	}

	/**
	* Check whether the reflog message should include the result of the update,
	* such as fast-forward or force-update.
	* <p>
	* Describes the default for commands in this batch that do not override it
	* with
	* {@link org.eclipse.jgit.transport.ReceiveCommand#setRefLogMessage(String, boolean)}.
	*
	* @return true if the message should include the result.
	*/
	public boolean isRefLogIncludingResult() {
	return refLogIncludeResult;
	}

	/**
	* Set the message to include in the reflog.
	* <p>
	* Repository implementations may limit which reflogs are written by
	* default, based on the project configuration. If a repo is not configured
	* to write logs for this ref by default, setting the message alone may have
	* no effect. To indicate that the repo should write logs for this update in
	* spite of configured defaults, use {@link #setForceRefLog(boolean)}.
	* <p>
	* Describes the default for commands in this batch that do not override it
	* with
	* {@link org.eclipse.jgit.transport.ReceiveCommand#setRefLogMessage(String, boolean)}.
	*
	* @param msg
	* the message to describe this change. If null and appendStatus
	* is false, the reflog will not be updated.
	* @param appendStatus
	* true if the status of the ref change (fast-forward or
	* forced-update) should be appended to the user supplied
	* message.
	* @return {@code this}.
	*/
	public BatchRefUpdate setRefLogMessage(String msg, boolean appendStatus) {
	if (msg == null && !appendStatus)
	disableRefLog();
	else if (msg == null && appendStatus) {
	refLogMessage = ""; //$NON-NLS-1$
	refLogIncludeResult = true;
	} else {
	refLogMessage = msg;
	refLogIncludeResult = appendStatus;
	}
	return this;
	}

	/**
	* Don't record this update in the ref's associated reflog.
	* <p>
	* Equivalent to {@code setRefLogMessage(null, false)}.
	*
	* @return {@code this}.
	*/
	public BatchRefUpdate disableRefLog() {
	refLogMessage = null;
	refLogIncludeResult = false;
	return this;
	}

	/**
	* Force writing a reflog for the updated ref.
	*
	* @param force whether to force.
	* @return {@code this}
	* @since 4.9
	*/
	public BatchRefUpdate setForceRefLog(boolean force) {
	forceRefLog = force;
	return this;
	}

	/**
	* Check whether log has been disabled by {@link #disableRefLog()}.
	*
	* @return true if disabled.
	*/
	public boolean isRefLogDisabled() {
	return refLogMessage == null;
	}

	/**
	* Check whether the reflog should be written regardless of repo defaults.
	*
	* @return whether force writing is enabled.
	* @since 4.9
	*/
	protected boolean isForceRefLog() {
	return forceRefLog;
	}

	/**
	* Request that all updates in this batch be performed atomically.
	* <p>
	* When atomic updates are used, either all commands apply successfully, or
	* none do. Commands that might have otherwise succeeded are rejected with
	* {@code REJECTED_OTHER_REASON}.
	* <p>
	* This method only works if the underlying ref database supports atomic
	* transactions, i.e.
	* {@link org.eclipse.jgit.lib.RefDatabase#performsAtomicTransactions()}
	* returns true. Calling this method with true if the underlying ref
	* database does not support atomic transactions will cause all commands to
	* fail with {@code
	* REJECTED_OTHER_REASON}.
	*
	* @param atomic
	* whether updates should be atomic.
	* @return {@code this}
	* @since 4.4
	*/
	public BatchRefUpdate setAtomic(boolean atomic) {
	this.atomic = atomic;
	return this;
	}

	/**
	* Whether updates should be atomic.
	*
	* @return atomic whether updates should be atomic.
	* @since 4.4
	*/
	public boolean isAtomic() {
	return atomic;
	}

	/**
	* Set a push certificate associated with this update.
	* <p>
	* This usually includes commands to update the refs in this batch, but is not
	* required to.
	*
	* @param cert
	* push certificate, may be null.
	* @since 4.1
	*/
	public void setPushCertificate(PushCertificate cert) {
	pushCert = cert;
	}

	/**
	* Set the push certificate associated with this update.
	* <p>
	* This usually includes commands to update the refs in this batch, but is not
	* required to.
	*
	* @return push certificate, may be null.
	* @since 4.1
	*/
	protected PushCertificate getPushCertificate() {
	return pushCert;
	}

	/**
	* Get commands this update will process.
	*
	* @return commands this update will process.
	*/
	public List<ReceiveCommand> getCommands() {
	return Collections.unmodifiableList(commands);
	}

	/**
	* Add a single command to this batch update.
	*
	* @param cmd
	* the command to add, must not be null.
	* @return {@code this}.
	*/
	public BatchRefUpdate addCommand(ReceiveCommand cmd) {
	commands.add(cmd);
	return this;
	}

	/**
	* Add commands to this batch update.
	*
	* @param cmd
	* the commands to add, must not be null.
	* @return {@code this}.
	*/
	public BatchRefUpdate addCommand(ReceiveCommand... cmd) {
	return addCommand(Arrays.asList(cmd));
	}

	/**
	* Add commands to this batch update.
	*
	* @param cmd
	* the commands to add, must not be null.
	* @return {@code this}.
	*/
	public BatchRefUpdate addCommand(Collection<ReceiveCommand> cmd) {
	commands.addAll(cmd);
	return this;
	}

	/**
	* Gets the list of option strings associated with this update.
	*
	* @return push options that were passed to {@link #execute}; prior to calling
	* {@link #execute}, always returns null.
	* @since 4.5
	*/
	@Nullable
	public List<String> getPushOptions() {
	return pushOptions;
	}

	/**
	* Set push options associated with this update.
	* <p>
	* Implementations must call this at the top of {@link #execute(RevWalk,
	* ProgressMonitor, List)}.
	*
	* @param options options passed to {@code execute}.
	* @since 4.9
	*/
	protected void setPushOptions(List<String> options) {
	pushOptions = options;
	}

	/**
	* Get list of timestamps the batch must wait for.
	*
	* @return list of timestamps the batch must wait for.
	* @since 4.6
	*/
	public List<ProposedTimestamp> getProposedTimestamps() {
	if (timestamps != null) {
	return Collections.unmodifiableList(timestamps);
	}
	return Collections.emptyList();
	}

	/**
	* Request the batch to wait for the affected timestamps to resolve.
	*
	* @param ts
	* a {@link org.eclipse.jgit.util.time.ProposedTimestamp} object.
	* @return {@code this}.
	* @since 4.6
	*/
	public BatchRefUpdate addProposedTimestamp(ProposedTimestamp ts) {
	if (timestamps == null) {
	timestamps = new ArrayList<>(4);
	}
	timestamps.add(ts);
	return this;
	}

	/**
	* Execute this batch update.
	* <p>
	* The default implementation of this method performs a sequential reference
	* update over each reference.
	* <p>
	* Implementations must respect the atomicity requirements of the underlying
	* database as described in {@link #setAtomic(boolean)} and
	* {@link org.eclipse.jgit.lib.RefDatabase#performsAtomicTransactions()}.
	*
	* @param walk
	* a RevWalk to parse tags in case the storage system wants to
	* store them pre-peeled, a common performance optimization.
	* @param monitor
	* progress monitor to receive update status on.
	* @param options
	* a list of option strings; set null to execute without
	* @throws java.io.IOException
	* the database is unable to accept the update. Individual
	* command status must be tested to determine if there is a
	* partial failure, or a total failure.
	* @since 4.5
	*/
	public void execute(RevWalk walk, ProgressMonitor monitor,
	List<String> options) throws IOException {

	if (atomic && !refdb.performsAtomicTransactions()) {
	for (ReceiveCommand c : commands) {
	if (c.getResult() == NOT_ATTEMPTED) {
	c.setResult(REJECTED_OTHER_REASON,
	JGitText.get().atomicRefUpdatesNotSupported);
	}
	}
	return;
	}
	if (!blockUntilTimestamps(MAX_WAIT)) {
	return;
	}

	if (options != null) {
	setPushOptions(options);
	}

	monitor.beginTask(JGitText.get().updatingReferences, commands.size());
	List<ReceiveCommand> commands2 = new ArrayList<>(
	commands.size());
	// First delete refs. This may free the name space for some of the
	// updates.
	for (ReceiveCommand cmd : commands) {
	try {
	if (cmd.getResult() == NOT_ATTEMPTED) {
	if (isMissing(walk, cmd.getOldId())
	\|\| isMissing(walk, cmd.getNewId())) {
	cmd.setResult(ReceiveCommand.Result.REJECTED_MISSING_OBJECT);
	continue;
	}
	cmd.updateType(walk);
	switch (cmd.getType()) {
	case CREATE:
	commands2.add(cmd);
	break;
	case UPDATE:
	case UPDATE_NONFASTFORWARD:
	commands2.add(cmd);
	break;
	case DELETE:
	RefUpdate rud = newUpdate(cmd);
	monitor.update(1);
	cmd.setResult(rud.delete(walk));
	}
	}
	} catch (IOException err) {
	cmd.setResult(
	REJECTED_OTHER_REASON,
	MessageFormat.format(JGitText.get().lockError,
	err.getMessage()));
	}
	}
	if (!commands2.isEmpty()) {
	// Perform updates that may require more room in the name space
	for (ReceiveCommand cmd : commands2) {
	try {
	if (cmd.getResult() == NOT_ATTEMPTED) {
	cmd.updateType(walk);
	RefUpdate ru = newUpdate(cmd);
	switch (cmd.getType()) {
	case DELETE:
	// Performed in the first phase
	break;
	case UPDATE:
	case UPDATE_NONFASTFORWARD:
	RefUpdate ruu = newUpdate(cmd);
	cmd.setResult(ruu.update(walk));
	break;
	case CREATE:
	cmd.setResult(ru.update(walk));
	break;
	}
	}
	} catch (IOException err) {
	cmd.setResult(REJECTED_OTHER_REASON, MessageFormat.format(
	JGitText.get().lockError, err.getMessage()));
	} finally {
	monitor.update(1);
	}
	}
	}
	monitor.endTask();
	}

	private static boolean isMissing(RevWalk walk, ObjectId id)
	throws IOException {
	if (id.equals(ObjectId.zeroId())) {
	return false; // Explicit add or delete is not missing.
	}
	try {
	walk.parseAny(id);
	return false;
	} catch (MissingObjectException e) {
	return true;
	}
	}

	/**
	* Wait for timestamps to be in the past, aborting commands on timeout.
	*
	* @param maxWait
	* maximum amount of time to wait for timestamps to resolve.
	* @return true if timestamps were successfully waited for; false if
	* commands were aborted.
	* @since 4.6
	*/
	protected boolean blockUntilTimestamps(Duration maxWait) {
	if (timestamps == null) {
	return true;
	}
	try {
	ProposedTimestamp.blockUntil(timestamps, maxWait);
	return true;
	} catch (TimeoutException \| InterruptedException e) {
	String msg = JGitText.get().timeIsUncertain;
	for (ReceiveCommand c : commands) {
	if (c.getResult() == NOT_ATTEMPTED) {
	c.setResult(REJECTED_OTHER_REASON, msg);
	}
	}
	return false;
	}
	}

	/**
	* Execute this batch update without option strings.
	*
	* @param walk
	* a RevWalk to parse tags in case the storage system wants to
	* store them pre-peeled, a common performance optimization.
	* @param monitor
	* progress monitor to receive update status on.
	* @throws java.io.IOException
	* the database is unable to accept the update. Individual
	* command status must be tested to determine if there is a
	* partial failure, or a total failure.
	*/
	public void execute(RevWalk walk, ProgressMonitor monitor)
	throws IOException {
	execute(walk, monitor, null);
	}

	/**
	* Get all path prefixes of a ref name.
	*
	* @param name
	* ref name.
	* @return path prefixes of the ref name. For {@code refs/heads/foo}, returns
	* {@code refs} and {@code refs/heads}.
	* @since 4.9
	*/
	protected static Collection<String> getPrefixes(String name) {
	Collection<String> ret = new HashSet<>();
	addPrefixesTo(name, ret);
	return ret;
	}

	/**
	* Add prefixes of a ref name to an existing collection.
	*
	* @param name
	* ref name.
	* @param out
	* path prefixes of the ref name. For {@code refs/heads/foo},
	* returns {@code refs} and {@code refs/heads}.
	* @since 4.9
	*/
	protected static void addPrefixesTo(String name, Collection<String> out) {
	int p1 = name.indexOf('/');
	while (p1 > 0) {
	out.add(name.substring(0, p1));
	p1 = name.indexOf('/', p1 + 1);
	}
	}

	/**
	* Create a new RefUpdate copying the batch settings.
	*
	* @param cmd
	* specific command the update should be created to copy.
	* @return a single reference update command.
	* @throws java.io.IOException
	* the reference database cannot make a new update object for
	* the given reference.
	*/
	protected RefUpdate newUpdate(ReceiveCommand cmd) throws IOException {
	RefUpdate ru = refdb.newUpdate(cmd.getRefName(), false);
	if (isRefLogDisabled(cmd)) {
	ru.disableRefLog();
	} else {
	ru.setRefLogIdent(refLogIdent);
	ru.setRefLogMessage(getRefLogMessage(cmd), isRefLogIncludingResult(cmd));
	ru.setForceRefLog(isForceRefLog(cmd));
	}
	ru.setPushCertificate(pushCert);
	switch (cmd.getType()) {
	case DELETE:
	if (!ObjectId.zeroId().equals(cmd.getOldId()))
	ru.setExpectedOldObjectId(cmd.getOldId());
	ru.setForceUpdate(true);
	return ru;

	case CREATE:
	case UPDATE:
	case UPDATE_NONFASTFORWARD:
	default:
	ru.setForceUpdate(isAllowNonFastForwards());
	ru.setExpectedOldObjectId(cmd.getOldId());
	ru.setNewObjectId(cmd.getNewId());
	return ru;
	}
	}

	/**
	* Check whether reflog is disabled for a command.
	*
	* @param cmd
	* specific command.
	* @return whether the reflog is disabled, taking into account the state from
	* this instance as well as overrides in the given command.
	* @since 4.9
	*/
	protected boolean isRefLogDisabled(ReceiveCommand cmd) {
	return cmd.hasCustomRefLog() ? cmd.isRefLogDisabled() : isRefLogDisabled();
	}

	/**
	* Get reflog message for a command.
	*
	* @param cmd
	* specific command.
	* @return reflog message, taking into account the state from this instance as
	* well as overrides in the given command.
	* @since 4.9
	*/
	protected String getRefLogMessage(ReceiveCommand cmd) {
	return cmd.hasCustomRefLog() ? cmd.getRefLogMessage() : getRefLogMessage();
	}

	/**
	* Check whether the reflog message for a command should include the result.
	*
	* @param cmd
	* specific command.
	* @return whether the reflog message should show the result, taking into
	* account the state from this instance as well as overrides in the
	* given command.
	* @since 4.9
	*/
	protected boolean isRefLogIncludingResult(ReceiveCommand cmd) {
	return cmd.hasCustomRefLog()
	? cmd.isRefLogIncludingResult() : isRefLogIncludingResult();
	}

	/**
	* Check whether the reflog for a command should be written regardless of repo
	* defaults.
	*
	* @param cmd
	* specific command.
	* @return whether force writing is enabled.
	* @since 4.9
	*/
	protected boolean isForceRefLog(ReceiveCommand cmd) {
	Boolean isForceRefLog = cmd.isForceRefLog();
	return isForceRefLog != null ? isForceRefLog.booleanValue()
	: isForceRefLog();
	}

	/** {@inheritDoc} */
	@Override
	public String toString() {
	StringBuilder r = new StringBuilder();
	r.append(getClass().getSimpleName()).append('[');
	if (commands.isEmpty())
	return r.append(']').toString();

	r.append('\n');
	for (ReceiveCommand cmd : commands) {
	r.append(" "); //$NON-NLS-1$
	r.append(cmd);
	r.append(" (").append(cmd.getResult()); //$NON-NLS-1$
	if (cmd.getMessage() != null) {
	r.append(": ").append(cmd.getMessage()); //$NON-NLS-1$
	}
	r.append(")\n"); //$NON-NLS-1$
	}
	return r.append(']').toString();
	}
	}