/*
    * Copyright (C) 2011-2018, Chris Aniszczyk <caniszczyk@gmail.com>
    * 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.
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   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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  package org.eclipse.jgit.api;
  
  import static java.time.Instant.EPOCH;
  import static org.eclipse.jgit.api.ResetCommand.ResetType.HARD;
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertFalse;
  import static org.junit.Assert.assertNotNull;
  import static org.junit.Assert.assertNull;
  import static org.junit.Assert.assertTrue;
  import static org.junit.Assert.fail;
  
  import java.io.File;
  import java.io.IOException;
  import java.nio.file.Files;
  import java.nio.file.attribute.FileTime;
  import java.time.Instant;
  
  import org.eclipse.jgit.api.ResetCommand.ResetType;
  import org.eclipse.jgit.api.errors.GitAPIException;
  import org.eclipse.jgit.api.errors.JGitInternalException;
  import org.eclipse.jgit.dircache.DirCache;
  import org.eclipse.jgit.dircache.DirCacheBuilder;
  import org.eclipse.jgit.dircache.DirCacheEntry;
  import org.eclipse.jgit.errors.AmbiguousObjectException;
  import org.eclipse.jgit.junit.RepositoryTestCase;
  import org.eclipse.jgit.lib.Constants;
  import org.eclipse.jgit.lib.FileMode;
  import org.eclipse.jgit.lib.ObjectId;
  import org.eclipse.jgit.lib.Ref;
  import org.eclipse.jgit.revwalk.RevCommit;
  import org.eclipse.jgit.revwalk.RevWalk;
  import org.eclipse.jgit.treewalk.TreeWalk;
  import org.eclipse.jgit.util.FileUtils;
  import org.junit.Assert;
  import org.junit.Test;
  
  public class ResetCommandTest extends RepositoryTestCase {
  
  	private Git git;
  
  	private RevCommit initialCommit;
  
  	private RevCommit secondCommit;
  
  	private File indexFile;
  
  	private File indexNestedFile;
  
  	private File untrackedFile;
  
  	private DirCacheEntry prestage;
  
  	public void setupRepository() throws IOException, JGitInternalException,
  			GitAPIException {
  
  		// create initial commit
  		git = new Git(db);
 		initialCommit = git.commit().setMessage("initial commit").call();
 
 		// create file
 		indexFile = writeTrashFile("a.txt", "content");
 
 		// create nested file
 		indexNestedFile = writeTrashFile("dir/b.txt", "content");
 
 		// add files and commit them
 		git.add().addFilepattern("a.txt").addFilepattern("dir/b.txt").call();
 		secondCommit = git.commit().setMessage("adding a.txt and dir/b.txt").call();
 
 		prestage = DirCache.read(db.getIndexFile(), db.getFS()).getEntry(indexFile.getName());
 
 		// modify files and add to index
 		writeTrashFile("a.txt", "new content");
 		writeTrashFile("dir/b.txt", "new content");
 		git.add().addFilepattern("a.txt").addFilepattern("dir/b.txt").call();
 
 		// create a file not added to the index
 		untrackedFile = writeTrashFile("notAddedToIndex.txt", "content");
 	}
 
 	@Test
 	public void testHardReset() throws JGitInternalException,
 			AmbiguousObjectException, IOException, GitAPIException {
 		setupRepository();
 		ObjectId prevHead = db.resolve(Constants.HEAD);
 		ResetCommand reset = git.reset();
 		assertSameAsHead(reset.setMode(ResetType.HARD)
 				.setRef(initialCommit.getName()).call());
 		assertFalse("reflog should be enabled", reset.isReflogDisabled());
 		// check if HEAD points to initial commit now
 		ObjectId head = db.resolve(Constants.HEAD);
 		assertEquals(initialCommit, head);
 		// check if files were removed
 		assertFalse(indexFile.exists());
 		assertFalse(indexNestedFile.exists());
 		assertTrue(untrackedFile.exists());
 		// fileInIndex must no longer be in HEAD and in the index
 		String fileInIndexPath = indexFile.getAbsolutePath();
 		assertFalse(inHead(fileInIndexPath));
 		assertFalse(inIndex(indexFile.getName()));
 		assertReflog(prevHead, head);
 		assertEquals(prevHead, db.readOrigHead());
 	}
 
 	@Test
 	public void testHardResetReflogDisabled() throws Exception {
 		setupRepository();
 		ObjectId prevHead = db.resolve(Constants.HEAD);
 		ResetCommand reset = git.reset();
 		assertSameAsHead(reset.setMode(ResetType.HARD)
 				.setRef(initialCommit.getName()).disableRefLog(true).call());
 		assertTrue("reflog should be disabled", reset.isReflogDisabled());
 		// check if HEAD points to initial commit now
 		ObjectId head = db.resolve(Constants.HEAD);
 		assertEquals(initialCommit, head);
 		// check if files were removed
 		assertFalse(indexFile.exists());
 		assertFalse(indexNestedFile.exists());
 		assertTrue(untrackedFile.exists());
 		// fileInIndex must no longer be in HEAD and in the index
 		String fileInIndexPath = indexFile.getAbsolutePath();
 		assertFalse(inHead(fileInIndexPath));
 		assertFalse(inIndex(indexFile.getName()));
 		assertReflogDisabled(head);
 		assertEquals(prevHead, db.readOrigHead());
 	}
 
 	@Test
 	public void testHardResetWithConflicts_OverwriteUntrackedFile() throws Exception {
 		setupRepository();
 
 		git.rm().setCached(true).addFilepattern("a.txt").call();
 		assertTrue(new File(db.getWorkTree(), "a.txt").exists());
 
 		git.reset().setMode(ResetType.HARD).setRef(Constants.HEAD).call();
 		assertTrue(new File(db.getWorkTree(), "a.txt").exists());
 		assertEquals("content", read(new File(db.getWorkTree(), "a.txt")));
 	}
 
 	@Test
 	public void testHardResetWithConflicts_DeleteFileFolderConflict() throws Exception {
 		setupRepository();
 
 		writeTrashFile("dir-or-file/c.txt", "content");
 		git.add().addFilepattern("dir-or-file/c.txt").call();
 
 		FileUtils.delete(new File(db.getWorkTree(), "dir-or-file"), FileUtils.RECURSIVE);
 		writeTrashFile("dir-or-file", "content");
 
 		git.reset().setMode(ResetType.HARD).setRef(Constants.HEAD).call();
 		assertFalse(new File(db.getWorkTree(), "dir-or-file").exists());
 	}
 
 	@Test
 	public void testResetToNonexistingHEAD() throws JGitInternalException,
 			AmbiguousObjectException, IOException, GitAPIException {
 
 		// create a file in the working tree of a fresh repo
 		git = new Git(db);
 		writeTrashFile("f", "content");
 
 		try {
 			git.reset().setRef(Constants.HEAD).call();
 			fail("Expected JGitInternalException didn't occur");
 		} catch (JGitInternalException e) {
 			// got the expected exception
 		}
 	}
 
 	@Test
 	public void testSoftReset() throws JGitInternalException,
 			AmbiguousObjectException, IOException, GitAPIException {
 		setupRepository();
 		ObjectId prevHead = db.resolve(Constants.HEAD);
 		assertSameAsHead(git.reset().setMode(ResetType.SOFT)
 				.setRef(initialCommit.getName()).call());
 		// check if HEAD points to initial commit now
 		ObjectId head = db.resolve(Constants.HEAD);
 		assertEquals(initialCommit, head);
 		// check if files still exist
 		assertTrue(untrackedFile.exists());
 		assertTrue(indexFile.exists());
 		// fileInIndex must no longer be in HEAD but has to be in the index
 		String fileInIndexPath = indexFile.getAbsolutePath();
 		assertFalse(inHead(fileInIndexPath));
 		assertTrue(inIndex(indexFile.getName()));
 		assertReflog(prevHead, head);
 		assertEquals(prevHead, db.readOrigHead());
 	}
 
 	@Test
 	public void testMixedReset() throws JGitInternalException,
 			AmbiguousObjectException, IOException, GitAPIException {
 		setupRepository();
 		ObjectId prevHead = db.resolve(Constants.HEAD);
 		assertSameAsHead(git.reset().setMode(ResetType.MIXED)
 				.setRef(initialCommit.getName()).call());
 		// check if HEAD points to initial commit now
 		ObjectId head = db.resolve(Constants.HEAD);
 		assertEquals(initialCommit, head);
 		// check if files still exist
 		assertTrue(untrackedFile.exists());
 		assertTrue(indexFile.exists());
 		// fileInIndex must no longer be in HEAD and in the index
 		String fileInIndexPath = indexFile.getAbsolutePath();
 		assertFalse(inHead(fileInIndexPath));
 		assertFalse(inIndex(indexFile.getName()));
 
 		assertReflog(prevHead, head);
 		assertEquals(prevHead, db.readOrigHead());
 	}
 
 	@Test
 	public void testMixedResetRetainsSizeAndModifiedTime() throws Exception {
 		git = new Git(db);
 
 		Files.setLastModifiedTime(writeTrashFile("a.txt", "a").toPath(),
 				FileTime.from(Instant.now().minusSeconds(60)));
 		assertNotNull(git.add().addFilepattern("a.txt").call());
 		assertNotNull(git.commit().setMessage("a commit").call());
 
 		Files.setLastModifiedTime(writeTrashFile("b.txt", "b").toPath(),
 				FileTime.from(Instant.now().minusSeconds(60)));
 		assertNotNull(git.add().addFilepattern("b.txt").call());
 		RevCommit commit2 = git.commit().setMessage("b commit").call();
 		assertNotNull(commit2);
 
 		DirCache cache = db.readDirCache();
 
 		DirCacheEntry aEntry = cache.getEntry("a.txt");
 		assertNotNull(aEntry);
 		assertTrue(aEntry.getLength() > 0);
 		assertTrue(aEntry.getLastModifiedInstant().compareTo(EPOCH) > 0);
 
 		DirCacheEntry bEntry = cache.getEntry("b.txt");
 		assertNotNull(bEntry);
 		assertTrue(bEntry.getLength() > 0);
 		assertTrue(bEntry.getLastModifiedInstant().compareTo(EPOCH) > 0);
 
 		assertSameAsHead(git.reset().setMode(ResetType.MIXED)
 				.setRef(commit2.getName()).call());
 
 		cache = db.readDirCache();
 
 		DirCacheEntry mixedAEntry = cache.getEntry("a.txt");
 		assertNotNull(mixedAEntry);
 		assertEquals(aEntry.getLastModifiedInstant(),
 				mixedAEntry.getLastModifiedInstant());
 		assertEquals(aEntry.getLastModifiedInstant(),
 				mixedAEntry.getLastModifiedInstant());
 
 		DirCacheEntry mixedBEntry = cache.getEntry("b.txt");
 		assertNotNull(mixedBEntry);
 		assertEquals(bEntry.getLastModifiedInstant(),
 				mixedBEntry.getLastModifiedInstant());
 		assertEquals(bEntry.getLastModifiedInstant(),
 				mixedBEntry.getLastModifiedInstant());
 	}
 
 	@Test
 	public void testMixedResetWithUnmerged() throws Exception {
 		git = new Git(db);
 
 		String file = "a.txt";
 		writeTrashFile(file, "data");
 		String file2 = "b.txt";
 		writeTrashFile(file2, "data");
 
 		git.add().addFilepattern(file).addFilepattern(file2).call();
 		git.commit().setMessage("commit").call();
 
 		DirCache index = db.lockDirCache();
 		DirCacheBuilder builder = index.builder();
 		builder.add(createEntry(file, FileMode.REGULAR_FILE, 1, ""));
 		builder.add(createEntry(file, FileMode.REGULAR_FILE, 2, ""));
 		builder.add(createEntry(file, FileMode.REGULAR_FILE, 3, ""));
 		assertTrue(builder.commit());
 
 		assertEquals("[a.txt, mode:100644, stage:1]"
 				+ "[a.txt, mode:100644, stage:2]"
 				+ "[a.txt, mode:100644, stage:3]",
 				indexState(0));
 
 		assertSameAsHead(git.reset().setMode(ResetType.MIXED).call());
 
 		assertEquals("[a.txt, mode:100644]" + "[b.txt, mode:100644]",
 				indexState(0));
 	}
 
 	@Test
 	public void testPathsReset() throws Exception {
 		setupRepository();
 
 		DirCacheEntry preReset = DirCache.read(db.getIndexFile(), db.getFS())
 				.getEntry(indexFile.getName());
 		assertNotNull(preReset);
 
 		git.add().addFilepattern(untrackedFile.getName()).call();
 
 		// 'a.txt' has already been modified in setupRepository
 		// 'notAddedToIndex.txt' has been added to repository
 		assertSameAsHead(git.reset().addPath(indexFile.getName())
 				.addPath(untrackedFile.getName()).call());
 
 		DirCacheEntry postReset = DirCache.read(db.getIndexFile(), db.getFS())
 				.getEntry(indexFile.getName());
 		assertNotNull(postReset);
 		Assert.assertNotSame(preReset.getObjectId(), postReset.getObjectId());
 		Assert.assertEquals(prestage.getObjectId(), postReset.getObjectId());
 
 		// check that HEAD hasn't moved
 		ObjectId head = db.resolve(Constants.HEAD);
 		assertEquals(secondCommit, head);
 		// check if files still exist
 		assertTrue(untrackedFile.exists());
 		assertTrue(indexFile.exists());
 		assertTrue(inHead(indexFile.getName()));
 		assertTrue(inIndex(indexFile.getName()));
 		assertFalse(inIndex(untrackedFile.getName()));
 	}
 
 	@Test
 	public void testPathsResetOnDirs() throws Exception {
 		setupRepository();
 
 		DirCacheEntry preReset = DirCache.read(db.getIndexFile(), db.getFS())
 				.getEntry("dir/b.txt");
 		assertNotNull(preReset);
 
 		git.add().addFilepattern(untrackedFile.getName()).call();
 
 		// 'dir/b.txt' has already been modified in setupRepository
 		assertSameAsHead(git.reset().addPath("dir").call());
 
 		DirCacheEntry postReset = DirCache.read(db.getIndexFile(), db.getFS())
 				.getEntry("dir/b.txt");
 		assertNotNull(postReset);
 		Assert.assertNotSame(preReset.getObjectId(), postReset.getObjectId());
 
 		// check that HEAD hasn't moved
 		ObjectId head = db.resolve(Constants.HEAD);
 		assertEquals(secondCommit, head);
 		// check if files still exist
 		assertTrue(untrackedFile.exists());
 		assertTrue(inHead("dir/b.txt"));
 		assertTrue(inIndex("dir/b.txt"));
 	}
 
 	@Test
 	public void testPathsResetWithRef() throws Exception {
 		setupRepository();
 
 		DirCacheEntry preReset = DirCache.read(db.getIndexFile(), db.getFS())
 				.getEntry(indexFile.getName());
 		assertNotNull(preReset);
 
 		git.add().addFilepattern(untrackedFile.getName()).call();
 
 		// 'a.txt' has already been modified in setupRepository
 		// 'notAddedToIndex.txt' has been added to repository
 		// reset to the inital commit
 		assertSameAsHead(git.reset().setRef(initialCommit.getName())
 				.addPath(indexFile.getName()).addPath(untrackedFile.getName())
 				.call());
 
 		// check that HEAD hasn't moved
 		ObjectId head = db.resolve(Constants.HEAD);
 		assertEquals(secondCommit, head);
 		// check if files still exist
 		assertTrue(untrackedFile.exists());
 		assertTrue(indexFile.exists());
 		assertTrue(inHead(indexFile.getName()));
 		assertFalse(inIndex(indexFile.getName()));
 		assertFalse(inIndex(untrackedFile.getName()));
 	}
 
 	@Test
 	public void testPathsResetWithUnmerged() throws Exception {
 		setupRepository();
 
 		String file = "a.txt";
 		writeTrashFile(file, "data");
 
 		git.add().addFilepattern(file).call();
 		git.commit().setMessage("commit").call();
 
 		DirCache index = db.lockDirCache();
 		DirCacheBuilder builder = index.builder();
 		builder.add(createEntry(file, FileMode.REGULAR_FILE, 1, ""));
 		builder.add(createEntry(file, FileMode.REGULAR_FILE, 2, ""));
 		builder.add(createEntry(file, FileMode.REGULAR_FILE, 3, ""));
 		builder.add(createEntry("b.txt", FileMode.REGULAR_FILE));
 		assertTrue(builder.commit());
 
 		assertEquals("[a.txt, mode:100644, stage:1]"
 				+ "[a.txt, mode:100644, stage:2]"
 				+ "[a.txt, mode:100644, stage:3]"
 				+ "[b.txt, mode:100644]",
 				indexState(0));
 
 		assertSameAsHead(git.reset().addPath(file).call());
 
 		assertEquals("[a.txt, mode:100644]" + "[b.txt, mode:100644]",
 				indexState(0));
 	}
 
 	@Test
 	public void testPathsResetOnUnbornBranch() throws Exception {
 		git = new Git(db);
 		writeTrashFile("a.txt", "content");
 		git.add().addFilepattern("a.txt").call();
 		// Should assume an empty tree, like in C Git 1.8.2
 		assertSameAsHead(git.reset().addPath("a.txt").call());
 
 		DirCache cache = db.readDirCache();
 		DirCacheEntry aEntry = cache.getEntry("a.txt");
 		assertNull(aEntry);
 	}
 
 	@Test(expected = JGitInternalException.class)
 	public void testPathsResetToNonexistingRef() throws Exception {
 		git = new Git(db);
 		writeTrashFile("a.txt", "content");
 		git.add().addFilepattern("a.txt").call();
 		assertSameAsHead(
 				git.reset().setRef("doesnotexist").addPath("a.txt").call());
 	}
 
 	@Test
 	public void testResetDefaultMode() throws Exception {
 		git = new Git(db);
 		writeTrashFile("a.txt", "content");
 		git.add().addFilepattern("a.txt").call();
 		writeTrashFile("a.txt", "modified");
 		// should use default mode MIXED
 		assertSameAsHead(git.reset().call());
 
 		DirCache cache = db.readDirCache();
 		DirCacheEntry aEntry = cache.getEntry("a.txt");
 		assertNull(aEntry);
 		assertEquals("modified", read("a.txt"));
 	}
 
 	@Test
 	public void testHardResetOnTag() throws Exception {
 		setupRepository();
 		String tagName = "initialtag";
 		git.tag().setName(tagName).setObjectId(secondCommit)
 				.setMessage("message").call();
 
 		DirCacheEntry preReset = DirCache.read(db.getIndexFile(), db.getFS())
 				.getEntry(indexFile.getName());
 		assertNotNull(preReset);
 
 		git.add().addFilepattern(untrackedFile.getName()).call();
 
 		assertSameAsHead(git.reset().setRef(tagName).setMode(HARD).call());
 
 		ObjectId head = db.resolve(Constants.HEAD);
 		assertEquals(secondCommit, head);
 	}
 
 	@Test
 	public void testHardResetAfterSquashMerge() throws Exception {
 		git = new Git(db);
 
 		writeTrashFile("file1", "file1");
 		git.add().addFilepattern("file1").call();
 		RevCommit first = git.commit().setMessage("initial commit").call();
 
 		assertTrue(new File(db.getWorkTree(), "file1").exists());
 		createBranch(first, "refs/heads/branch1");
 		checkoutBranch("refs/heads/branch1");
 
 		writeTrashFile("file2", "file2");
 		git.add().addFilepattern("file2").call();
 		git.commit().setMessage("second commit").call();
 		assertTrue(new File(db.getWorkTree(), "file2").exists());
 
 		checkoutBranch("refs/heads/master");
 
 		MergeResult result = git.merge()
 				.include(db.exactRef("refs/heads/branch1"))
 				.setSquash(true)
 				.call();
 
 		assertEquals(MergeResult.MergeStatus.FAST_FORWARD_SQUASHED,
 				result.getMergeStatus());
 		assertNotNull(db.readSquashCommitMsg());
 
 		assertSameAsHead(git.reset().setMode(ResetType.HARD)
 				.setRef(first.getName()).call());
 
 		assertNull(db.readSquashCommitMsg());
 	}
 
 	@Test
 	public void testHardResetOnUnbornBranch() throws Exception {
 		git = new Git(db);
 		File fileA = writeTrashFile("a.txt", "content");
 		git.add().addFilepattern("a.txt").call();
 		// Should assume an empty tree, like in C Git 1.8.2
 		assertSameAsHead(git.reset().setMode(ResetType.HARD).call());
 
 		DirCache cache = db.readDirCache();
 		DirCacheEntry aEntry = cache.getEntry("a.txt");
 		assertNull(aEntry);
 		assertFalse(fileA.exists());
 		assertNull(db.resolve(Constants.HEAD));
 	}
 
 	private void assertReflog(ObjectId prevHead, ObjectId head)
 			throws IOException {
 		// Check the reflog for HEAD
 		String actualHeadMessage = db.getReflogReader(Constants.HEAD)
 				.getLastEntry().getComment();
 		String expectedHeadMessage = head.getName() + ": updating HEAD";
 		assertEquals(expectedHeadMessage, actualHeadMessage);
 		assertEquals(head.getName(), db.getReflogReader(Constants.HEAD)
 				.getLastEntry().getNewId().getName());
 		assertEquals(prevHead.getName(), db.getReflogReader(Constants.HEAD)
 				.getLastEntry().getOldId().getName());
 
 		// The reflog for master contains the same as the one for HEAD
 		String actualMasterMessage = db.getReflogReader("refs/heads/master")
 				.getLastEntry().getComment();
 		String expectedMasterMessage = head.getName() + ": updating HEAD"; // yes!
 		assertEquals(expectedMasterMessage, actualMasterMessage);
 		assertEquals(head.getName(), db.getReflogReader(Constants.HEAD)
 				.getLastEntry().getNewId().getName());
 		assertEquals(prevHead.getName(), db
 				.getReflogReader("refs/heads/master").getLastEntry().getOldId()
 				.getName());
 	}
 
 	private void assertReflogDisabled(ObjectId head)
 			throws IOException {
 		// Check the reflog for HEAD
 		String actualHeadMessage = db.getReflogReader(Constants.HEAD)
 				.getLastEntry().getComment();
 		String expectedHeadMessage = "commit: adding a.txt and dir/b.txt";
 		assertEquals(expectedHeadMessage, actualHeadMessage);
 		assertEquals(head.getName(), db.getReflogReader(Constants.HEAD)
 				.getLastEntry().getOldId().getName());
 
 		// The reflog for master contains the same as the one for HEAD
 		String actualMasterMessage = db.getReflogReader("refs/heads/master")
 				.getLastEntry().getComment();
 		String expectedMasterMessage = "commit: adding a.txt and dir/b.txt";
 		assertEquals(expectedMasterMessage, actualMasterMessage);
 		assertEquals(head.getName(), db.getReflogReader(Constants.HEAD)
 				.getLastEntry().getOldId().getName());
 	}
 	/**
 	 * Checks if a file with the given path exists in the HEAD tree
 	 *
 	 * @param path
 	 * @return true if the file exists
 	 * @throws IOException
 	 */
 	private boolean inHead(String path) throws IOException {
 		ObjectId headId = db.resolve(Constants.HEAD);
 		try (RevWalk rw = new RevWalk(db);
 				TreeWalk tw = TreeWalk.forPath(db, path,
 						rw.parseTree(headId))) {
 			return tw != null;
 		}
 	}
 
 	/**
 	 * Checks if a file with the given path exists in the index
 	 *
 	 * @param path
 	 * @return true if the file exists
 	 * @throws IOException
 	 */
 	private boolean inIndex(String path) throws IOException {
 		DirCache dc = DirCache.read(db.getIndexFile(), db.getFS());
 		return dc.getEntry(path) != null;
 	}
 
 	/**
 	 * Asserts that a certain ref is similar to repos HEAD.
 	 * @param ref
 	 * @throws IOException
 	 */
 	private void assertSameAsHead(Ref ref) throws IOException {
 		Ref headRef = db.exactRef(Constants.HEAD);
 		assertEquals(headRef.getName(), ref.getName());
 		assertEquals(headRef.getObjectId(), ref.getObjectId());
 	}
 }