/*
    * Copyright (C) 2010, Christian Halstrick <christian.halstrick@sap.com>
    * Copyright (C) 2010, 2014, Stefan Lay <stefan.lay@sap.com>
    * Copyright (C) 2016, 2021 Laurent Delaigue <laurent.delaigue@obeo.fr> 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.api;
  
  import java.io.IOException;
  import java.text.MessageFormat;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.Locale;
  import java.util.Map;
  
  import org.eclipse.jgit.annotations.Nullable;
  import org.eclipse.jgit.api.MergeResult.MergeStatus;
  import org.eclipse.jgit.api.errors.CheckoutConflictException;
  import org.eclipse.jgit.api.errors.ConcurrentRefUpdateException;
  import org.eclipse.jgit.api.errors.GitAPIException;
  import org.eclipse.jgit.api.errors.InvalidMergeHeadsException;
  import org.eclipse.jgit.api.errors.JGitInternalException;
  import org.eclipse.jgit.api.errors.NoHeadException;
  import org.eclipse.jgit.api.errors.NoMessageException;
  import org.eclipse.jgit.api.errors.WrongRepositoryStateException;
  import org.eclipse.jgit.dircache.DirCacheCheckout;
  import org.eclipse.jgit.events.WorkingTreeModifiedEvent;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.lib.AnyObjectId;
  import org.eclipse.jgit.lib.Config.ConfigEnum;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.NullProgressMonitor;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.ObjectIdRef;
  import org.eclipse.jgit.lib.ProgressMonitor;
  import org.eclipse.jgit.lib.Ref;
  import org.eclipse.jgit.lib.Ref.Storage;
  import org.eclipse.jgit.lib.RefUpdate;
  import org.eclipse.jgit.lib.RefUpdate.Result;
  import org.eclipse.jgit.lib.Repository;
  import org.eclipse.jgit.merge.ContentMergeStrategy;
  import org.eclipse.jgit.merge.MergeConfig;
  import org.eclipse.jgit.merge.MergeMessageFormatter;
  import org.eclipse.jgit.merge.MergeStrategy;
  import org.eclipse.jgit.merge.Merger;
  import org.eclipse.jgit.merge.ResolveMerger;
  import org.eclipse.jgit.merge.ResolveMerger.MergeFailureReason;
  import org.eclipse.jgit.merge.SquashMessageFormatter;
  import org.eclipse.jgit.revwalk.RevCommit;
  import org.eclipse.jgit.revwalk.RevWalk;
  import org.eclipse.jgit.revwalk.RevWalkUtils;
  import org.eclipse.jgit.treewalk.FileTreeIterator;
  import org.eclipse.jgit.util.StringUtils;
  
  /**
   * A class used to execute a {@code Merge} command. It has setters for all
   * supported options and arguments of this command and a {@link #call()} method
   * to finally execute the command. Each instance of this class should only be
   * used for one invocation of the command (means: one call to {@link #call()})
   *
   * @see <a href="http://www.kernel.org/pub/software/scm/git/docs/git-merge.html"
   *      >Git documentation about Merge</a>
   */
  public class MergeCommand extends GitCommand<MergeResult> {
  
  	private MergeStrategy mergeStrategy = MergeStrategy.RECURSIVE;
  
  	private ContentMergeStrategy contentStrategy;
  
  	private List<Ref> commits = new LinkedList<>();
  
  	private Boolean squash;
  
  	private FastForwardMode fastForwardMode;
  
  	private String message;
  
  	private boolean insertChangeId;
  
  	private ProgressMonitor monitor = NullProgressMonitor.INSTANCE;
  
  	/**
  	 * Values for the "merge.conflictStyle" git config.
  	 *
  	 * @since 5.12
  	 */
  	public enum ConflictStyle {
  
  		/** "merge" style: only ours/theirs. This is the default. */
  		MERGE,
  
  		/** "diff3" style: ours/base/theirs. */
 		DIFF3
 	}
 
 	/**
 	 * The modes available for fast forward merges corresponding to the
 	 * <code>--ff</code>, <code>--no-ff</code> and <code>--ff-only</code>
 	 * options under <code>branch.&lt;name&gt;.mergeoptions</code>.
 	 */
 	public enum FastForwardMode implements ConfigEnum {
 		/**
 		 * Corresponds to the default --ff option (for a fast forward update the
 		 * branch pointer only).
 		 */
 		FF,
 		/**
 		 * Corresponds to the --no-ff option (create a merge commit even for a
 		 * fast forward).
 		 */
 		NO_FF,
 		/**
 		 * Corresponds to the --ff-only option (abort unless the merge is a fast
 		 * forward).
 		 */
 		FF_ONLY;
 
 		@Override
 		public String toConfigValue() {
 			return "--" + name().toLowerCase(Locale.ROOT).replace('_', '-'); //$NON-NLS-1$
 		}
 
 		@Override
 		public boolean matchConfigValue(String in) {
 			if (StringUtils.isEmptyOrNull(in))
 				return false;
 			if (!in.startsWith("--")) //$NON-NLS-1$
 				return false;
 			return name().equalsIgnoreCase(in.substring(2).replace('-', '_'));
 		}
 
 		/**
 		 * The modes available for fast forward merges corresponding to the
 		 * options under <code>merge.ff</code>.
 		 */
 		public enum Merge {
 			/**
 			 * {@link FastForwardMode#FF}.
 			 */
 			TRUE,
 			/**
 			 * {@link FastForwardMode#NO_FF}.
 			 */
 			FALSE,
 			/**
 			 * {@link FastForwardMode#FF_ONLY}.
 			 */
 			ONLY;
 
 			/**
 			 * Map from <code>FastForwardMode</code> to
 			 * <code>FastForwardMode.Merge</code>.
 			 *
 			 * @param ffMode
 			 *            the <code>FastForwardMode</code> value to be mapped
 			 * @return the mapped <code>FastForwardMode.Merge</code> value
 			 */
 			public static Merge valueOf(FastForwardMode ffMode) {
 				switch (ffMode) {
 				case NO_FF:
 					return FALSE;
 				case FF_ONLY:
 					return ONLY;
 				default:
 					return TRUE;
 				}
 			}
 		}
 
 		/**
 		 * Map from <code>FastForwardMode.Merge</code> to
 		 * <code>FastForwardMode</code>.
 		 *
 		 * @param ffMode
 		 *            the <code>FastForwardMode.Merge</code> value to be mapped
 		 * @return the mapped <code>FastForwardMode</code> value
 		 */
 		public static FastForwardMode valueOf(FastForwardMode.Merge ffMode) {
 			switch (ffMode) {
 			case FALSE:
 				return NO_FF;
 			case ONLY:
 				return FF_ONLY;
 			default:
 				return FF;
 			}
 		}
 	}
 
 	private Boolean commit;
 
 	/**
 	 * Constructor for MergeCommand.
 	 *
 	 * @param repo
 	 *            the {@link org.eclipse.jgit.lib.Repository}
 	 */
 	protected MergeCommand(Repository repo) {
 		super(repo);
 	}
 
 	/**
 	 * {@inheritDoc}
 	 * <p>
 	 * Execute the {@code Merge} command with all the options and parameters
 	 * collected by the setter methods (e.g. {@link #include(Ref)}) of this
 	 * class. Each instance of this class should only be used for one invocation
 	 * of the command. Don't call this method twice on an instance.
 	 */
 	@Override
 	@SuppressWarnings("boxing")
 	public MergeResult call() throws GitAPIException, NoHeadException,
 			ConcurrentRefUpdateException, CheckoutConflictException,
 			InvalidMergeHeadsException, WrongRepositoryStateException, NoMessageException {
 		checkCallable();
 		fallBackToConfiguration();
 		checkParameters();
 
 		DirCacheCheckout dco = null;
 		try (RevWalklk.html#RevWalk">RevWalk revWalk = new RevWalk(repo)) {
 			Ref head = repo.exactRef(Constants.HEAD);
 			if (head == null)
 				throw new NoHeadException(
 						JGitText.get().commitOnRepoWithoutHEADCurrentlyNotSupported);
 			StringBuilder refLogMessage = new StringBuilder("merge "); //$NON-NLS-1$
 
 			// Check for FAST_FORWARD, ALREADY_UP_TO_DATE
 
 			// we know for now there is only one commit
 			Ref ref = commits.get(0);
 
 			refLogMessage.append(ref.getName());
 
 			// handle annotated tags
 			ref = repo.getRefDatabase().peel(ref);
 			ObjectId objectId = ref.getPeeledObjectId();
 			if (objectId == null)
 				objectId = ref.getObjectId();
 
 			RevCommit srcCommit = revWalk.lookupCommit(objectId);
 
 			ObjectId headId = head.getObjectId();
 			if (headId == null) {
 				revWalk.parseHeaders(srcCommit);
 				dco = new DirCacheCheckout(repo,
 						repo.lockDirCache(), srcCommit.getTree());
 				dco.setFailOnConflict(true);
 				dco.setProgressMonitor(monitor);
 				dco.checkout();
 				RefUpdate refUpdate = repo
 						.updateRef(head.getTarget().getName());
 				refUpdate.setNewObjectId(objectId);
 				refUpdate.setExpectedOldObjectId(null);
 				refUpdate.setRefLogMessage("initial pull", false); //$NON-NLS-1$
 				if (refUpdate.update() != Result.NEW)
 					throw new NoHeadException(
 							JGitText.get().commitOnRepoWithoutHEADCurrentlyNotSupported);
 				setCallable(false);
 				return new MergeResult(srcCommit, srcCommit, new ObjectId[] {
 						null, srcCommit }, MergeStatus.FAST_FORWARD,
 						mergeStrategy, null, null);
 			}
 
 			RevCommit headCommit = revWalk.lookupCommit(headId);
 
 			if (revWalk.isMergedInto(srcCommit, headCommit)) {
 				setCallable(false);
 				return new MergeResult(headCommit, srcCommit, new ObjectId[] {
 						headCommit, srcCommit },
 						MergeStatus.ALREADY_UP_TO_DATE, mergeStrategy, null, null);
 			} else if (revWalk.isMergedInto(headCommit, srcCommit)
 					&& fastForwardMode != FastForwardMode.NO_FF) {
 				// FAST_FORWARD detected: skip doing a real merge but only
 				// update HEAD
 				refLogMessage.append(": " + MergeStatus.FAST_FORWARD); //$NON-NLS-1$
 				dco = new DirCacheCheckout(repo,
 						headCommit.getTree(), repo.lockDirCache(),
 						srcCommit.getTree());
 				dco.setProgressMonitor(monitor);
 				dco.setFailOnConflict(true);
 				dco.checkout();
 				String msg = null;
 				ObjectId newHead, base = null;
 				MergeStatus mergeStatus = null;
 				if (!squash) {
 					updateHead(refLogMessage, srcCommit, headId);
 					newHead = base = srcCommit;
 					mergeStatus = MergeStatus.FAST_FORWARD;
 				} else {
 					msg = JGitText.get().squashCommitNotUpdatingHEAD;
 					newHead = base = headId;
 					mergeStatus = MergeStatus.FAST_FORWARD_SQUASHED;
 					List<RevCommit> squashedCommits = RevWalkUtils.find(
 							revWalk, srcCommit, headCommit);
 					String squashMessage = new SquashMessageFormatter().format(
 							squashedCommits, head);
 					repo.writeSquashCommitMsg(squashMessage);
 				}
 				setCallable(false);
 				return new MergeResult(newHead, base, new ObjectId[] {
 						headCommit, srcCommit }, mergeStatus, mergeStrategy,
 						null, msg);
 			} else {
 				if (fastForwardMode == FastForwardMode.FF_ONLY) {
 					return new MergeResult(headCommit, srcCommit,
 							new ObjectId[] { headCommit, srcCommit },
 							MergeStatus.ABORTED, mergeStrategy, null, null);
 				}
 				String mergeMessage = ""; //$NON-NLS-1$
 				if (!squash) {
 					if (message != null)
 						mergeMessage = message;
 					else
 						mergeMessage = new MergeMessageFormatter().format(
 							commits, head);
 					repo.writeMergeCommitMsg(mergeMessage);
 					repo.writeMergeHeads(Arrays.asList(ref.getObjectId()));
 				} else {
 					List<RevCommit> squashedCommits = RevWalkUtils.find(
 							revWalk, srcCommit, headCommit);
 					String squashMessage = new SquashMessageFormatter().format(
 							squashedCommits, head);
 					repo.writeSquashCommitMsg(squashMessage);
 				}
 				Merger merger = mergeStrategy.newMerger(repo);
 				merger.setProgressMonitor(monitor);
 				boolean noProblems;
 				Map<String, org.eclipse.jgit.merge.MergeResult<?>> lowLevelResults = null;
 				Map<String, MergeFailureReason> failingPaths = null;
 				List<String> unmergedPaths = null;
 				if (merger instanceof ResolveMerger) {
 					ResolveMerger resolveMerger = (ResolveMerger) merger;
 					resolveMerger.setContentMergeStrategy(contentStrategy);
 					resolveMerger.setCommitNames(new String[] {
 							"BASE", "HEAD", ref.getName() }); //$NON-NLS-1$ //$NON-NLS-2$
 					resolveMerger.setWorkingTreeIterator(new FileTreeIterator(repo));
 					noProblems = merger.merge(headCommit, srcCommit);
 					lowLevelResults = resolveMerger
 							.getMergeResults();
 					failingPaths = resolveMerger.getFailingPaths();
 					unmergedPaths = resolveMerger.getUnmergedPaths();
 					if (!resolveMerger.getModifiedFiles().isEmpty()) {
 						repo.fireEvent(new WorkingTreeModifiedEvent(
 								resolveMerger.getModifiedFiles(), null));
 					}
 				} else
 					noProblems = merger.merge(headCommit, srcCommit);
 				refLogMessage.append(": Merge made by "); //$NON-NLS-1$
 				if (!revWalk.isMergedInto(headCommit, srcCommit))
 					refLogMessage.append(mergeStrategy.getName());
 				else
 					refLogMessage.append("recursive"); //$NON-NLS-1$
 				refLogMessage.append('.');
 				if (noProblems) {
 					dco = new DirCacheCheckout(repo,
 							headCommit.getTree(), repo.lockDirCache(),
 							merger.getResultTreeId());
 					dco.setFailOnConflict(true);
 					dco.setProgressMonitor(monitor);
 					dco.checkout();
 
 					String msg = null;
 					ObjectId newHeadId = null;
 					MergeStatus mergeStatus = null;
 					if (!commit && squash) {
 						mergeStatus = MergeStatus.MERGED_SQUASHED_NOT_COMMITTED;
 					}
 					if (!commit && !squash) {
 						mergeStatus = MergeStatus.MERGED_NOT_COMMITTED;
 					}
 					if (commit && !squash) {
 						try (Gitit.html#Git">Git git = new Git(getRepository())) {
 							newHeadId = git.commit()
 									.setReflogComment(refLogMessage.toString())
 									.setInsertChangeId(insertChangeId)
 									.call().getId();
 						}
 						mergeStatus = MergeStatus.MERGED;
 						getRepository().autoGC(monitor);
 					}
 					if (commit && squash) {
 						msg = JGitText.get().squashCommitNotUpdatingHEAD;
 						newHeadId = headCommit.getId();
 						mergeStatus = MergeStatus.MERGED_SQUASHED;
 					}
 					return new MergeResult(newHeadId, null,
 							new ObjectId[] { headCommit.getId(),
 									srcCommit.getId() }, mergeStatus,
 							mergeStrategy, null, msg);
 				}
 				if (failingPaths != null) {
 					repo.writeMergeCommitMsg(null);
 					repo.writeMergeHeads(null);
 					return new MergeResult(null, merger.getBaseCommitId(),
 							new ObjectId[] { headCommit.getId(),
 									srcCommit.getId() },
 							MergeStatus.FAILED, mergeStrategy, lowLevelResults,
 							failingPaths, null);
 				}
 				String mergeMessageWithConflicts = new MergeMessageFormatter()
 						.formatWithConflicts(mergeMessage, unmergedPaths);
 				repo.writeMergeCommitMsg(mergeMessageWithConflicts);
 				return new MergeResult(null, merger.getBaseCommitId(),
 						new ObjectId[] { headCommit.getId(),
 								srcCommit.getId() },
 						MergeStatus.CONFLICTING, mergeStrategy, lowLevelResults,
 						null);
 			}
 		} catch (org.eclipse.jgit.errors.CheckoutConflictException e) {
 			List<String> conflicts = (dco == null) ? Collections
 					.<String> emptyList() : dco.getConflicts();
 			throw new CheckoutConflictException(conflicts, e);
 		} catch (IOException e) {
 			throw new JGitInternalException(
 					MessageFormat.format(
 							JGitText.get().exceptionCaughtDuringExecutionOfMergeCommand,
 							e), e);
 		}
 	}
 
 	private void checkParameters() throws InvalidMergeHeadsException {
 		if (squash.booleanValue() && fastForwardMode == FastForwardMode.NO_FF) {
 			throw new JGitInternalException(
 					JGitText.get().cannotCombineSquashWithNoff);
 		}
 
 		if (commits.size() != 1)
 			throw new InvalidMergeHeadsException(
 					commits.isEmpty() ? JGitText.get().noMergeHeadSpecified
 							: MessageFormat.format(
 									JGitText.get().mergeStrategyDoesNotSupportHeads,
 									mergeStrategy.getName(),
 									Integer.valueOf(commits.size())));
 	}
 
 	/**
 	 * Use values from the configuration if they have not been explicitly
 	 * defined via the setters
 	 */
 	private void fallBackToConfiguration() {
 		MergeConfig config = MergeConfig.getConfigForCurrentBranch(repo);
 		if (squash == null)
 			squash = Boolean.valueOf(config.isSquash());
 		if (commit == null)
 			commit = Boolean.valueOf(config.isCommit());
 		if (fastForwardMode == null)
 			fastForwardMode = config.getFastForwardMode();
 	}
 
 	private void updateHead(StringBuilder refLogMessage, ObjectId newHeadId,
 			ObjectId oldHeadID) throws IOException,
 			ConcurrentRefUpdateException {
 		RefUpdate refUpdate = repo.updateRef(Constants.HEAD);
 		refUpdate.setNewObjectId(newHeadId);
 		refUpdate.setRefLogMessage(refLogMessage.toString(), false);
 		refUpdate.setExpectedOldObjectId(oldHeadID);
 		Result rc = refUpdate.update();
 		switch (rc) {
 		case NEW:
 		case FAST_FORWARD:
 			return;
 		case REJECTED:
 		case LOCK_FAILURE:
 			throw new ConcurrentRefUpdateException(
 					JGitText.get().couldNotLockHEAD, refUpdate.getRef(), rc);
 		default:
 			throw new JGitInternalException(MessageFormat.format(
 					JGitText.get().updatingRefFailed, Constants.HEAD,
 					newHeadId.toString(), rc));
 		}
 	}
 
 	/**
 	 * Set merge strategy
 	 *
 	 * @param mergeStrategy
 	 *            the {@link org.eclipse.jgit.merge.MergeStrategy} to be used
 	 * @return {@code this}
 	 */
 	public MergeCommand setStrategy(MergeStrategy mergeStrategy) {
 		checkCallable();
 		this.mergeStrategy = mergeStrategy;
 		return this;
 	}
 
 	/**
 	 * Sets the content merge strategy to use if the
 	 * {@link #setStrategy(MergeStrategy) merge strategy} is "resolve" or
 	 * "recursive".
 	 *
 	 * @param strategy
 	 *            the {@link ContentMergeStrategy} to be used
 	 * @return {@code this}
 	 * @since 5.12
 	 */
 	public MergeCommand setContentMergeStrategy(ContentMergeStrategy strategy) {
 		checkCallable();
 		this.contentStrategy = strategy;
 		return this;
 	}
 
 	/**
 	 * Reference to a commit to be merged with the current head
 	 *
 	 * @param aCommit
 	 *            a reference to a commit which is merged with the current head
 	 * @return {@code this}
 	 */
 	public MergeCommand include(Ref aCommit) {
 		checkCallable();
 		commits.add(aCommit);
 		return this;
 	}
 
 	/**
 	 * Id of a commit which is to be merged with the current head
 	 *
 	 * @param aCommit
 	 *            the Id of a commit which is merged with the current head
 	 * @return {@code this}
 	 */
 	public MergeCommand include(AnyObjectId aCommit) {
 		return include(aCommit.getName(), aCommit);
 	}
 
 	/**
 	 * Include a commit
 	 *
 	 * @param name
 	 *            a name of a {@code Ref} pointing to the commit
 	 * @param aCommit
 	 *            the Id of a commit which is merged with the current head
 	 * @return {@code this}
 	 */
 	public MergeCommand include(String name, AnyObjectId aCommit) {
 		return include(new ObjectIdRef.Unpeeled(Storage.LOOSE, name,
 				aCommit.copy()));
 	}
 
 	/**
 	 * If <code>true</code>, will prepare the next commit in working tree and
 	 * index as if a real merge happened, but do not make the commit or move the
 	 * HEAD. Otherwise, perform the merge and commit the result.
 	 * <p>
 	 * In case the merge was successful but this flag was set to
 	 * <code>true</code> a {@link org.eclipse.jgit.api.MergeResult} with status
 	 * {@link org.eclipse.jgit.api.MergeResult.MergeStatus#MERGED_SQUASHED} or
 	 * {@link org.eclipse.jgit.api.MergeResult.MergeStatus#FAST_FORWARD_SQUASHED}
 	 * is returned.
 	 *
 	 * @param squash
 	 *            whether to squash commits or not
 	 * @return {@code this}
 	 * @since 2.0
 	 */
 	public MergeCommand setSquash(boolean squash) {
 		checkCallable();
 		this.squash = Boolean.valueOf(squash);
 		return this;
 	}
 
 	/**
 	 * Sets the fast forward mode.
 	 *
 	 * @param fastForwardMode
 	 *            corresponds to the --ff/--no-ff/--ff-only options. If
 	 *            {@code null} use the value of the {@code merge.ff} option
 	 *            configured in git config. If this option is not configured
 	 *            --ff is the built-in default.
 	 * @return {@code this}
 	 * @since 2.2
 	 */
 	public MergeCommand setFastForward(
 			@Nullable FastForwardMode fastForwardMode) {
 		checkCallable();
 		this.fastForwardMode = fastForwardMode;
 		return this;
 	}
 
 	/**
 	 * Controls whether the merge command should automatically commit after a
 	 * successful merge
 	 *
 	 * @param commit
 	 *            <code>true</code> if this command should commit (this is the
 	 *            default behavior). <code>false</code> if this command should
 	 *            not commit. In case the merge was successful but this flag was
 	 *            set to <code>false</code> a
 	 *            {@link org.eclipse.jgit.api.MergeResult} with type
 	 *            {@link org.eclipse.jgit.api.MergeResult} with status
 	 *            {@link org.eclipse.jgit.api.MergeResult.MergeStatus#MERGED_NOT_COMMITTED}
 	 *            is returned
 	 * @return {@code this}
 	 * @since 3.0
 	 */
 	public MergeCommand setCommit(boolean commit) {
 		this.commit = Boolean.valueOf(commit);
 		return this;
 	}
 
 	/**
 	 * Set the commit message to be used for the merge commit (in case one is
 	 * created)
 	 *
 	 * @param message
 	 *            the message to be used for the merge commit
 	 * @return {@code this}
 	 * @since 3.5
 	 */
 	public MergeCommand setMessage(String message) {
 		this.message = message;
 		return this;
 	}
 
 	/**
 	 * If set to true a change id will be inserted into the commit message
 	 *
 	 * An existing change id is not replaced. An initial change id (I000...)
 	 * will be replaced by the change id.
 	 *
 	 * @param insertChangeId
 	 *            whether to insert a change id
 	 * @return {@code this}
 	 * @since 5.0
 	 */
 	public MergeCommand setInsertChangeId(boolean insertChangeId) {
 		checkCallable();
 		this.insertChangeId = insertChangeId;
 		return this;
 	}
 
 	/**
 	 * The progress monitor associated with the diff operation. By default, this
 	 * is set to <code>NullProgressMonitor</code>
 	 *
 	 * @see NullProgressMonitor
 	 * @param monitor
 	 *            A progress monitor
 	 * @return this instance
 	 * @since 4.2
 	 */
 	public MergeCommand setProgressMonitor(ProgressMonitor monitor) {
 		if (monitor == null) {
 			monitor = NullProgressMonitor.INSTANCE;
 		}
 		this.monitor = monitor;
 		return this;
 	}
 }