org.eclipse.jgit/src/org/eclipse/jgit/api/MergeCommand.java - sop/jgit - Git at Google

 /*
  * Copyright (C) 2010, Christian Halstrick <christian.halstrick@sap.com>
  * Copyright (C) 2010-2014, Stefan Lay <stefan.lay@sap.com>
  * Copyright (C) 2016, Laurent Delaigue <laurent.delaigue@obeo.fr>
  * and other copyright owners as documented in the project's IP log.
  *
  * This program and the accompanying materials are made available
  * under the terms of the Eclipse Distribution License v1.0 which
  * accompanies this distribution, is reproduced below, and is
  * available at http://www.eclipse.org/org/documents/edl-v10.php
  *
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or
  * without modification, are permitted provided that the following
  * conditions are met:
  *
  * - Redistributions of source code must retain the above copyright
  *   notice, this list of conditions and the following disclaimer.
  *
  * - Redistributions in binary form must reproduce the above
  *   copyright notice, this list of conditions and the following
  *   disclaimer in the documentation and/or other materials provided
  *   with the distribution.
  *
  * - Neither the name of the Eclipse Foundation, Inc. nor the
  *   names of its contributors may be used to endorse or promote
  *   products derived from this software without specific prior
  *   written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 package org.eclipse.jgit.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.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 List<Ref> commits = new LinkedList<>();

 	private Boolean squash;

 	private FastForwardMode fastForwardMode;

 	private String message;

 	private ProgressMonitor monitor = NullProgressMonitor.INSTANCE;

 	/**
 	 * 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;

 	/**
 	 * @param repo
 	 */
 	protected MergeCommand(Repository repo) {
 		super(repo);
 	}

 	/**
 	 * Executes 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.
 	 *
 	 * @return the result of the merge
 	 */
 	@Override
 	@SuppressWarnings("boxing")
 	public MergeResult call() throws GitAPIException, NoHeadException,
 			ConcurrentRefUpdateException, CheckoutConflictException,
 			InvalidMergeHeadsException, WrongRepositoryStateException, NoMessageException {
 		checkCallable();
 		fallBackToConfiguration();
 		checkParameters();

 		RevWalk revWalk = null;
 		DirCacheCheckout dco = null;
 		try {
 			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
 			revWalk = new RevWalk(repo);

 			// we know for now there is only one commit
 			Ref ref = commits.get(0);

 			refLogMessage.append(ref.getName());

 			// handle annotated tags
 			ref = repo.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.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.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.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.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 (Git git = new Git(getRepository())) {
 							newHeadId = git.commit()
 									.setReflogComment(refLogMessage.toString())
 									.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);
 				} else {
 					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);
 					} else {
 						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);
 		} finally {
 			if (revWalk != null)
 				revWalk.close();
 		}
 	}

 	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 configuation 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));
 		}
 	}

 	/**
 	 *
 	 * @param mergeStrategy
 	 *            the {@link MergeStrategy} to be used
 	 * @return {@code this}
 	 */
 	public MergeCommand setStrategy(MergeStrategy mergeStrategy) {
 		checkCallable();
 		this.mergeStrategy = mergeStrategy;
 		return this;
 	}

 	/**
 	 * @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;
 	}

 	/**
 	 * @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);
 	}

 	/**
 	 * @param name
 	 *            a name given 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 MergeResult} with status
 	 * {@link MergeStatus#MERGED_SQUASHED} or
 	 * {@link 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 MergeResult} with type
 	 *            {@link MergeResult} with status
 	 *            {@link 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;
 	}

 	/**
 	 * 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;
 	}
 }
	/*
	* Copyright (C) 2010, Christian Halstrick <christian.halstrick@sap.com>
	* Copyright (C) 2010-2014, Stefan Lay <stefan.lay@sap.com>
	* Copyright (C) 2016, Laurent Delaigue <laurent.delaigue@obeo.fr>
	* and other copyright owners as documented in the project's IP log.
	*
	* This program and the accompanying materials are made available
	* under the terms of the Eclipse Distribution License v1.0 which
	* accompanies this distribution, is reproduced below, and is
	* available at http://www.eclipse.org/org/documents/edl-v10.php
	*
	* All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or
	* without modification, are permitted provided that the following
	* conditions are met:
	*
	* - Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	*
	* - Redistributions in binary form must reproduce the above
	* copyright notice, this list of conditions and the following
	* disclaimer in the documentation and/or other materials provided
	* with the distribution.
	*
	* - Neither the name of the Eclipse Foundation, Inc. nor the
	* names of its contributors may be used to endorse or promote
	* products derived from this software without specific prior
	* written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
	* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
	* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
	* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
	* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
	* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
	* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
	* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/
	package org.eclipse.jgit.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.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 List<Ref> commits = new LinkedList<>();

	private Boolean squash;

	private FastForwardMode fastForwardMode;

	private String message;

	private ProgressMonitor monitor = NullProgressMonitor.INSTANCE;

	/**
	* 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.<name>.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;

	/**
	* @param repo
	*/
	protected MergeCommand(Repository repo) {
	super(repo);
	}

	/**
	* Executes 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.
	*
	* @return the result of the merge
	*/
	@Override
	@SuppressWarnings("boxing")
	public MergeResult call() throws GitAPIException, NoHeadException,
	ConcurrentRefUpdateException, CheckoutConflictException,
	InvalidMergeHeadsException, WrongRepositoryStateException, NoMessageException {
	checkCallable();
	fallBackToConfiguration();
	checkParameters();

	RevWalk revWalk = null;
	DirCacheCheckout dco = null;
	try {
	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
	revWalk = new RevWalk(repo);

	// we know for now there is only one commit
	Ref ref = commits.get(0);

	refLogMessage.append(ref.getName());

	// handle annotated tags
	ref = repo.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.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.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.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.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 (Git git = new Git(getRepository())) {
	newHeadId = git.commit()
	.setReflogComment(refLogMessage.toString())
	.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);
	} else {
	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);
	} else {
	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);
	} finally {
	if (revWalk != null)
	revWalk.close();
	}
	}

	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 configuation 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));
	}
	}

	/**
	*
	* @param mergeStrategy
	* the {@link MergeStrategy} to be used
	* @return {@code this}
	*/
	public MergeCommand setStrategy(MergeStrategy mergeStrategy) {
	checkCallable();
	this.mergeStrategy = mergeStrategy;
	return this;
	}

	/**
	* @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;
	}

	/**
	* @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);
	}

	/**
	* @param name
	* a name given 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 MergeResult} with status
	* {@link MergeStatus#MERGED_SQUASHED} or
	* {@link 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 MergeResult} with type
	* {@link MergeResult} with status
	* {@link 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;
	}

	/**
	* 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;
	}
	}