/*
    * Copyright (C) 2007, Dave Watson <dwatson@mimvista.com>
    * Copyright (C) 2007-2008, Robin Rosenberg <robin.rosenberg@dewire.com>
    * Copyright (C) 2010, Jens Baumgart <jens.baumgart@sap.com>
    * Copyright (C) 2013, Robin Stocker <robin@nibor.org>
    * Copyright (C) 2014, Axel Richard <axel.richard@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.lib;
  
  import java.io.IOException;
  import java.text.MessageFormat;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  
  import org.eclipse.jgit.dircache.DirCache;
  import org.eclipse.jgit.dircache.DirCacheEntry;
  import org.eclipse.jgit.dircache.DirCacheIterator;
  import org.eclipse.jgit.errors.ConfigInvalidException;
  import org.eclipse.jgit.errors.IncorrectObjectTypeException;
  import org.eclipse.jgit.errors.MissingObjectException;
  import org.eclipse.jgit.errors.StopWalkException;
  import org.eclipse.jgit.internal.JGitText;
  import org.eclipse.jgit.revwalk.RevWalk;
  import org.eclipse.jgit.submodule.SubmoduleWalk;
  import org.eclipse.jgit.submodule.SubmoduleWalk.IgnoreSubmoduleMode;
  import org.eclipse.jgit.treewalk.AbstractTreeIterator;
  import org.eclipse.jgit.treewalk.EmptyTreeIterator;
  import org.eclipse.jgit.treewalk.FileTreeIterator;
  import org.eclipse.jgit.treewalk.TreeWalk;
  import org.eclipse.jgit.treewalk.TreeWalk.OperationType;
  import org.eclipse.jgit.treewalk.WorkingTreeIterator;
  import org.eclipse.jgit.treewalk.filter.AndTreeFilter;
  import org.eclipse.jgit.treewalk.filter.IndexDiffFilter;
  import org.eclipse.jgit.treewalk.filter.SkipWorkTreeFilter;
  import org.eclipse.jgit.treewalk.filter.TreeFilter;
  
  /**
   * Compares the index, a tree, and the working directory Ignored files are not
   * taken into account. The following information is retrieved:
   * <ul>
   * <li>added files</li>
   * <li>changed files</li>
   * <li>removed files</li>
   * <li>missing files</li>
   * <li>modified files</li>
   * <li>conflicting files</li>
   * <li>untracked files</li>
   * <li>files with assume-unchanged flag</li>
   * </ul>
   */
  public class IndexDiff {
  
  	/**
  	 * Represents the state of the index for a certain path regarding the stages
 	 * - which stages exist for a path and which not (base, ours, theirs).
 	 * <p>
 	 * This is used for figuring out what kind of conflict occurred.
 	 *
 	 * @see IndexDiff#getConflictingStageStates()
 	 * @since 3.0
 	 */
 	public static enum StageState {
 		/**
 		 * Exists in base, but neither in ours nor in theirs.
 		 */
 		BOTH_DELETED(1),
 
 		/**
 		 * Only exists in ours.
 		 */
 		ADDED_BY_US(2),
 
 		/**
 		 * Exists in base and ours, but no in theirs.
 		 */
 		DELETED_BY_THEM(3),
 
 		/**
 		 * Only exists in theirs.
 		 */
 		ADDED_BY_THEM(4),
 
 		/**
 		 * Exists in base and theirs, but not in ours.
 		 */
 		DELETED_BY_US(5),
 
 		/**
 		 * Exists in ours and theirs, but not in base.
 		 */
 		BOTH_ADDED(6),
 
 		/**
 		 * Exists in all stages, content conflict.
 		 */
 		BOTH_MODIFIED(7);
 
 		private final int stageMask;
 
 		private StageState(int stageMask) {
 			this.stageMask = stageMask;
 		}
 
 		int getStageMask() {
 			return stageMask;
 		}
 
 		/**
 		 * @return whether there is a "base" stage entry
 		 */
 		public boolean hasBase() {
 			return (stageMask & 1) != 0;
 		}
 
 		/**
 		 * @return whether there is an "ours" stage entry
 		 */
 		public boolean hasOurs() {
 			return (stageMask & 2) != 0;
 		}
 
 		/**
 		 * @return whether there is a "theirs" stage entry
 		 */
 		public boolean hasTheirs() {
 			return (stageMask & 4) != 0;
 		}
 
 		static StageState fromMask(int stageMask) {
 			// bits represent: theirs, ours, base
 			switch (stageMask) {
 			case 1: // 0b001
 				return BOTH_DELETED;
 			case 2: // 0b010
 				return ADDED_BY_US;
 			case 3: // 0b011
 				return DELETED_BY_THEM;
 			case 4: // 0b100
 				return ADDED_BY_THEM;
 			case 5: // 0b101
 				return DELETED_BY_US;
 			case 6: // 0b110
 				return BOTH_ADDED;
 			case 7: // 0b111
 				return BOTH_MODIFIED;
 			default:
 				return null;
 			}
 		}
 	}
 
 	private static final class ProgressReportingFilter extends TreeFilter {
 
 		private final ProgressMonitor monitor;
 
 		private int count = 0;
 
 		private int stepSize;
 
 		private final int total;
 
 		private ProgressReportingFilter(ProgressMonitor monitor, int total) {
 			this.monitor = monitor;
 			this.total = total;
 			stepSize = total / 100;
 			if (stepSize == 0)
 				stepSize = 1000;
 		}
 
 		@Override
 		public boolean shouldBeRecursive() {
 			return false;
 		}
 
 		@Override
 		public boolean include(TreeWalk walker)
 				throws MissingObjectException,
 				IncorrectObjectTypeException, IOException {
 			count++;
 			if (count % stepSize == 0) {
 				if (count <= total)
 					monitor.update(stepSize);
 				if (monitor.isCancelled())
 					throw StopWalkException.INSTANCE;
 			}
 			return true;
 		}
 
 		@Override
 		public TreeFilter clone() {
 			throw new IllegalStateException(
 					"Do not clone this kind of filter: " //$NON-NLS-1$
 							+ getClass().getName());
 		}
 	}
 
 	private final static int TREE = 0;
 
 	private final static int INDEX = 1;
 
 	private final static int WORKDIR = 2;
 
 	private final Repository repository;
 
 	private final AnyObjectId tree;
 
 	private TreeFilter filter = null;
 
 	private final WorkingTreeIterator initialWorkingTreeIterator;
 
 	private Set<String> added = new HashSet<>();
 
 	private Set<String> changed = new HashSet<>();
 
 	private Set<String> removed = new HashSet<>();
 
 	private Set<String> missing = new HashSet<>();
 
 	private Set<String> modified = new HashSet<>();
 
 	private Set<String> untracked = new HashSet<>();
 
 	private Map<String, StageState> conflicts = new HashMap<>();
 
 	private Set<String> ignored;
 
 	private Set<String> assumeUnchanged;
 
 	private DirCache dirCache;
 
 	private IndexDiffFilter indexDiffFilter;
 
 	private Map<String, IndexDiff> submoduleIndexDiffs = new HashMap<>();
 
 	private IgnoreSubmoduleMode ignoreSubmoduleMode = null;
 
 	private Map<FileMode, Set<String>> fileModes = new HashMap<>();
 
 	/**
 	 * Construct an IndexDiff
 	 *
 	 * @param repository
 	 *            a {@link org.eclipse.jgit.lib.Repository} object.
 	 * @param revstr
 	 *            symbolic name e.g. HEAD An EmptyTreeIterator is used if
 	 *            <code>revstr</code> cannot be resolved.
 	 * @param workingTreeIterator
 	 *            iterator for working directory
 	 * @throws java.io.IOException
 	 */
 	public IndexDiff(Repository repository, String revstr,
 			WorkingTreeIterator workingTreeIterator) throws IOException {
 		this(repository, repository.resolve(revstr), workingTreeIterator);
 	}
 
 	/**
 	 * Construct an Indexdiff
 	 *
 	 * @param repository
 	 *            a {@link org.eclipse.jgit.lib.Repository} object.
 	 * @param objectId
 	 *            tree id. If null, an EmptyTreeIterator is used.
 	 * @param workingTreeIterator
 	 *            iterator for working directory
 	 * @throws java.io.IOException
 	 */
 	public IndexDiff(Repository repository, ObjectId objectId,
 			WorkingTreeIterator workingTreeIterator) throws IOException {
 		this.repository = repository;
 		if (objectId != null) {
 			try (RevWalk rw = new RevWalk(repository)) {
 				tree = rw.parseTree(objectId);
 			}
 		} else {
 			tree = null;
 		}
 		this.initialWorkingTreeIterator = workingTreeIterator;
 	}
 
 	/**
 	 * Defines how modifications in submodules are treated
 	 *
 	 * @param mode
 	 *            defines how modifications in submodules are treated
 	 * @since 3.6
 	 */
 	public void setIgnoreSubmoduleMode(IgnoreSubmoduleMode mode) {
 		this.ignoreSubmoduleMode = mode;
 	}
 
 	/**
 	 * A factory to producing WorkingTreeIterators
 	 * @since 3.6
 	 */
 	public interface WorkingTreeIteratorFactory {
 		/**
 		 * @param repo
 		 *            the repository
 		 * @return working tree iterator
 		 */
 		public WorkingTreeIterator getWorkingTreeIterator(Repository repo);
 	}
 
 	private WorkingTreeIteratorFactory wTreeIt = new WorkingTreeIteratorFactory() {
 		@Override
 		public WorkingTreeIterator getWorkingTreeIterator(Repository repo) {
 			return new FileTreeIterator(repo);
 		}
 	};
 
 	/**
 	 * Allows higher layers to set the factory for WorkingTreeIterators.
 	 *
 	 * @param wTreeIt
 	 * @since 3.6
 	 */
 	public void setWorkingTreeItFactory(WorkingTreeIteratorFactory wTreeIt) {
 		this.wTreeIt = wTreeIt;
 	}
 
 	/**
 	 * Sets a filter. Can be used e.g. for restricting the tree walk to a set of
 	 * files.
 	 *
 	 * @param filter
 	 *            a {@link org.eclipse.jgit.treewalk.filter.TreeFilter} object.
 	 */
 	public void setFilter(TreeFilter filter) {
 		this.filter = filter;
 	}
 
 	/**
 	 * Run the diff operation. Until this is called, all lists will be empty.
 	 * Use {@link #diff(ProgressMonitor, int, int, String)} if a progress
 	 * monitor is required.
 	 *
 	 * @return if anything is different between index, tree, and workdir
 	 * @throws java.io.IOException
 	 */
 	public boolean diff() throws IOException {
 		return diff(null, 0, 0, ""); //$NON-NLS-1$
 	}
 
 	/**
 	 * Run the diff operation. Until this is called, all lists will be empty.
 	 * <p>
 	 * The operation may be aborted by the progress monitor. In that event it
 	 * will report what was found before the cancel operation was detected.
 	 * Callers should ignore the result if monitor.isCancelled() is true. If a
 	 * progress monitor is not needed, callers should use {@link #diff()}
 	 * instead. Progress reporting is crude and approximate and only intended
 	 * for informing the user.
 	 *
 	 * @param monitor
 	 *            for reporting progress, may be null
 	 * @param estWorkTreeSize
 	 *            number or estimated files in the working tree
 	 * @param estIndexSize
 	 *            number of estimated entries in the cache
 	 * @param title a {@link java.lang.String} object.
 	 * @return if anything is different between index, tree, and workdir
 	 * @throws java.io.IOException
 	 */
 	public boolean diff(final ProgressMonitor monitor, int estWorkTreeSize,
 			int estIndexSize, final String title)
 			throws IOException {
 		dirCache = repository.readDirCache();
 
 		try (TreeWalk treeWalk = new TreeWalk(repository)) {
 			treeWalk.setOperationType(OperationType.CHECKIN_OP);
 			treeWalk.setRecursive(true);
 			// add the trees (tree, dirchache, workdir)
 			if (tree != null)
 				treeWalk.addTree(tree);
 			else
 				treeWalk.addTree(new EmptyTreeIterator());
 			treeWalk.addTree(new DirCacheIterator(dirCache));
 			treeWalk.addTree(initialWorkingTreeIterator);
 			initialWorkingTreeIterator.setDirCacheIterator(treeWalk, 1);
 			Collection<TreeFilter> filters = new ArrayList<>(4);
 
 			if (monitor != null) {
 				// Get the maximum size of the work tree and index
 				// and add some (quite arbitrary)
 				if (estIndexSize == 0)
 					estIndexSize = dirCache.getEntryCount();
 				int total = Math.max(estIndexSize * 10 / 9,
 						estWorkTreeSize * 10 / 9);
 				monitor.beginTask(title, total);
 				filters.add(new ProgressReportingFilter(monitor, total));
 			}
 
 			if (filter != null)
 				filters.add(filter);
 			filters.add(new SkipWorkTreeFilter(INDEX));
 			indexDiffFilter = new IndexDiffFilter(INDEX, WORKDIR);
 			filters.add(indexDiffFilter);
 			treeWalk.setFilter(AndTreeFilter.create(filters));
 			fileModes.clear();
 			while (treeWalk.next()) {
 				AbstractTreeIterator treeIterator = treeWalk.getTree(TREE,
 						AbstractTreeIterator.class);
 				DirCacheIterator dirCacheIterator = treeWalk.getTree(INDEX,
 						DirCacheIterator.class);
 				WorkingTreeIterator workingTreeIterator = treeWalk
 						.getTree(WORKDIR, WorkingTreeIterator.class);
 
 				if (dirCacheIterator != null) {
 					final DirCacheEntry dirCacheEntry = dirCacheIterator
 							.getDirCacheEntry();
 					if (dirCacheEntry != null) {
 						int stage = dirCacheEntry.getStage();
 						if (stage > 0) {
 							String path = treeWalk.getPathString();
 							addConflict(path, stage);
 							continue;
 						}
 					}
 				}
 
 				if (treeIterator != null) {
 					if (dirCacheIterator != null) {
 						if (!treeIterator.idEqual(dirCacheIterator)
 								|| treeIterator
 										.getEntryRawMode() != dirCacheIterator
 												.getEntryRawMode()) {
 							// in repo, in index, content diff => changed
 							if (!isEntryGitLink(treeIterator)
 									|| !isEntryGitLink(dirCacheIterator)
 									|| ignoreSubmoduleMode != IgnoreSubmoduleMode.ALL)
 								changed.add(treeWalk.getPathString());
 						}
 					} else {
 						// in repo, not in index => removed
 						if (!isEntryGitLink(treeIterator)
 								|| ignoreSubmoduleMode != IgnoreSubmoduleMode.ALL)
 							removed.add(treeWalk.getPathString());
 						if (workingTreeIterator != null)
 							untracked.add(treeWalk.getPathString());
 					}
 				} else {
 					if (dirCacheIterator != null) {
 						// not in repo, in index => added
 						if (!isEntryGitLink(dirCacheIterator)
 								|| ignoreSubmoduleMode != IgnoreSubmoduleMode.ALL)
 							added.add(treeWalk.getPathString());
 					} else {
 						// not in repo, not in index => untracked
 						if (workingTreeIterator != null
 								&& !workingTreeIterator.isEntryIgnored()) {
 							untracked.add(treeWalk.getPathString());
 						}
 					}
 				}
 
 				if (dirCacheIterator != null) {
 					if (workingTreeIterator == null) {
 						// in index, not in workdir => missing
 						if (!isEntryGitLink(dirCacheIterator)
 								|| ignoreSubmoduleMode != IgnoreSubmoduleMode.ALL)
 							missing.add(treeWalk.getPathString());
 					} else {
 						if (workingTreeIterator.isModified(
 								dirCacheIterator.getDirCacheEntry(), true,
 								treeWalk.getObjectReader())) {
 							// in index, in workdir, content differs => modified
 							if (!isEntryGitLink(dirCacheIterator)
 									|| !isEntryGitLink(workingTreeIterator)
 									|| (ignoreSubmoduleMode != IgnoreSubmoduleMode.ALL
 											&& ignoreSubmoduleMode != IgnoreSubmoduleMode.DIRTY))
 								modified.add(treeWalk.getPathString());
 						}
 					}
 				}
 
 				String path = treeWalk.getPathString();
 				if (path != null) {
 					for (int i = 0; i < treeWalk.getTreeCount(); i++) {
 						recordFileMode(path, treeWalk.getFileMode(i));
 					}
 				}
 			}
 		}
 
 		if (ignoreSubmoduleMode != IgnoreSubmoduleMode.ALL) {
 			IgnoreSubmoduleMode localIgnoreSubmoduleMode = ignoreSubmoduleMode;
 			SubmoduleWalk smw = SubmoduleWalk.forIndex(repository);
 			while (smw.next()) {
 				try {
 					if (localIgnoreSubmoduleMode == null)
 						localIgnoreSubmoduleMode = smw.getModulesIgnore();
 					if (IgnoreSubmoduleMode.ALL
 							.equals(localIgnoreSubmoduleMode))
 						continue;
 				} catch (ConfigInvalidException e) {
 					throw new IOException(MessageFormat.format(
 							JGitText.get().invalidIgnoreParamSubmodule,
 							smw.getPath()), e);
 				}
 				try (Repository subRepo = smw.getRepository()) {
 					if (subRepo != null) {
 						String subRepoPath = smw.getPath();
 						ObjectId subHead = subRepo.resolve("HEAD"); //$NON-NLS-1$
 						if (subHead != null
 								&& !subHead.equals(smw.getObjectId())) {
 							modified.add(subRepoPath);
 							recordFileMode(subRepoPath, FileMode.GITLINK);
 						} else if (ignoreSubmoduleMode != IgnoreSubmoduleMode.DIRTY) {
 							IndexDiff smid = submoduleIndexDiffs.get(smw
 									.getPath());
 							if (smid == null) {
 								smid = new IndexDiff(subRepo,
 										smw.getObjectId(),
 										wTreeIt.getWorkingTreeIterator(subRepo));
 								submoduleIndexDiffs.put(subRepoPath, smid);
 							}
 							if (smid.diff()) {
 								if (ignoreSubmoduleMode == IgnoreSubmoduleMode.UNTRACKED
 										&& smid.getAdded().isEmpty()
 										&& smid.getChanged().isEmpty()
 										&& smid.getConflicting().isEmpty()
 										&& smid.getMissing().isEmpty()
 										&& smid.getModified().isEmpty()
 										&& smid.getRemoved().isEmpty()) {
 									continue;
 								}
 								modified.add(subRepoPath);
 								recordFileMode(subRepoPath, FileMode.GITLINK);
 							}
 						}
 					}
 				}
 			}
 
 		}
 
 		// consume the remaining work
 		if (monitor != null)
 			monitor.endTask();
 
 		ignored = indexDiffFilter.getIgnoredPaths();
 		if (added.isEmpty() && changed.isEmpty() && removed.isEmpty()
 				&& missing.isEmpty() && modified.isEmpty()
 				&& untracked.isEmpty())
 			return false;
 		else
 			return true;
 	}
 
 	private void recordFileMode(String path, FileMode mode) {
 		Set<String> values = fileModes.get(mode);
 		if (path != null) {
 			if (values == null) {
 				values = new HashSet<>();
 				fileModes.put(mode, values);
 			}
 			values.add(path);
 		}
 	}
 
 	private boolean isEntryGitLink(AbstractTreeIterator ti) {
 		return ((ti != null) && (ti.getEntryRawMode() == FileMode.GITLINK
 				.getBits()));
 	}
 
 	private void addConflict(String path, int stage) {
 		StageState existingStageStates = conflicts.get(path);
 		byte stageMask = 0;
 		if (existingStageStates != null)
 			stageMask |= existingStageStates.getStageMask();
 		// stage 1 (base) should be shifted 0 times
 		int shifts = stage - 1;
 		stageMask |= (1 << shifts);
 		StageState stageState = StageState.fromMask(stageMask);
 		conflicts.put(path, stageState);
 	}
 
 	/**
 	 * Get list of files added to the index, not in the tree
 	 *
 	 * @return list of files added to the index, not in the tree
 	 */
 	public Set<String> getAdded() {
 		return added;
 	}
 
 	/**
 	 * Get list of files changed from tree to index
 	 *
 	 * @return list of files changed from tree to index
 	 */
 	public Set<String> getChanged() {
 		return changed;
 	}
 
 	/**
 	 * Get list of files removed from index, but in tree
 	 *
 	 * @return list of files removed from index, but in tree
 	 */
 	public Set<String> getRemoved() {
 		return removed;
 	}
 
 	/**
 	 * Get list of files in index, but not filesystem
 	 *
 	 * @return list of files in index, but not filesystem
 	 */
 	public Set<String> getMissing() {
 		return missing;
 	}
 
 	/**
 	 * Get list of files modified on disk relative to the index
 	 *
 	 * @return list of files modified on disk relative to the index
 	 */
 	public Set<String> getModified() {
 		return modified;
 	}
 
 	/**
 	 * Get list of files that are not ignored, and not in the index.
 	 *
 	 * @return list of files that are not ignored, and not in the index.
 	 */
 	public Set<String> getUntracked() {
 		return untracked;
 	}
 
 	/**
 	 * Get list of files that are in conflict, corresponds to the keys of
 	 * {@link #getConflictingStageStates()}
 	 *
 	 * @return list of files that are in conflict, corresponds to the keys of
 	 *         {@link #getConflictingStageStates()}
 	 */
 	public Set<String> getConflicting() {
 		return conflicts.keySet();
 	}
 
 	/**
 	 * Get the map from each path of {@link #getConflicting()} to its
 	 * corresponding {@link org.eclipse.jgit.lib.IndexDiff.StageState}
 	 *
 	 * @return the map from each path of {@link #getConflicting()} to its
 	 *         corresponding {@link org.eclipse.jgit.lib.IndexDiff.StageState}
 	 * @since 3.0
 	 */
 	public Map<String, StageState> getConflictingStageStates() {
 		return conflicts;
 	}
 
 	/**
 	 * The method returns the list of ignored files and folders. Only the root
 	 * folder of an ignored folder hierarchy is reported. If a/b/c is listed in
 	 * the .gitignore then you should not expect a/b/c/d/e/f to be reported
 	 * here. Only a/b/c will be reported. Furthermore only ignored files /
 	 * folders are returned that are NOT in the index.
 	 *
 	 * @return list of files / folders that are ignored
 	 */
 	public Set<String> getIgnoredNotInIndex() {
 		return ignored;
 	}
 
 	/**
 	 * Get list of files with the flag assume-unchanged
 	 *
 	 * @return list of files with the flag assume-unchanged
 	 */
 	public Set<String> getAssumeUnchanged() {
 		if (assumeUnchanged == null) {
 			HashSet<String> unchanged = new HashSet<>();
 			for (int i = 0; i < dirCache.getEntryCount(); i++)
 				if (dirCache.getEntry(i).isAssumeValid())
 					unchanged.add(dirCache.getEntry(i).getPathString());
 			assumeUnchanged = unchanged;
 		}
 		return assumeUnchanged;
 	}
 
 	/**
 	 * Get list of folders containing only untracked files/folders
 	 *
 	 * @return list of folders containing only untracked files/folders
 	 */
 	public Set<String> getUntrackedFolders() {
 		return ((indexDiffFilter == null) ? Collections.<String> emptySet()
 				: new HashSet<>(indexDiffFilter.getUntrackedFolders()));
 	}
 
 	/**
 	 * Get the file mode of the given path in the index
 	 *
 	 * @param path a {@link java.lang.String} object.
 	 * @return file mode
 	 */
 	public FileMode getIndexMode(String path) {
 		final DirCacheEntry entry = dirCache.getEntry(path);
 		return entry != null ? entry.getFileMode() : FileMode.MISSING;
 	}
 
 	/**
 	 * Get the list of paths that IndexDiff has detected to differ and have the
 	 * given file mode
 	 *
 	 * @param mode a {@link org.eclipse.jgit.lib.FileMode} object.
 	 * @return the list of paths that IndexDiff has detected to differ and have
 	 *         the given file mode
 	 * @since 3.6
 	 */
 	public Set<String> getPathsWithIndexMode(FileMode mode) {
 		Set<String> paths = fileModes.get(mode);
 		if (paths == null)
 			paths = new HashSet<>();
 		return paths;
 	}
 }