/*
    * Copyright (C) 2012, IBM Corporation
    * 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.pgm;
  
  import static org.junit.Assert.assertArrayEquals;
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertFalse;
  import static org.junit.Assert.assertNotNull;
  import static org.junit.Assert.assertTrue;
  import static org.junit.Assert.fail;
  
  import java.io.File;
  import java.nio.file.Files;
  import java.nio.file.Path;
  import java.util.Arrays;
  import java.util.List;
  
  import org.eclipse.jgit.api.Git;
  import org.eclipse.jgit.api.errors.CheckoutConflictException;
  import org.eclipse.jgit.diff.DiffEntry;
  import org.eclipse.jgit.lib.CLIRepositoryTestCase;
  import org.eclipse.jgit.lib.FileMode;
  import org.eclipse.jgit.lib.Ref;
  import org.eclipse.jgit.revwalk.RevCommit;
  import org.eclipse.jgit.treewalk.FileTreeIterator;
  import org.eclipse.jgit.treewalk.FileTreeIterator.FileEntry;
  import org.eclipse.jgit.treewalk.TreeWalk;
  import org.eclipse.jgit.util.FS;
  import org.eclipse.jgit.util.FileUtils;
  import org.junit.Assume;
  import org.junit.Test;
  
  public class CheckoutTest extends CLIRepositoryTestCase {
  	/**
  	 * Executes specified git command (with arguments), captures exception and
  	 * returns its message as an array of lines. Throws an AssertionError if no
  	 * exception is thrown.
  	 *
  	 * @param command
  	 *            a valid git command line, e.g. "git branch -h"
  	 * @return message contained within the exception
  	 */
  	private String[] executeExpectingException(String command) {
  		try {
  			execute(command);
  			throw new AssertionError("Expected Die");
  		} catch (Exception e) {
  			return e.getMessage().split(System.lineSeparator());
  		}
  	}
  
  	@Test
  	public void testCheckoutSelf() throws Exception {
  		try (Git git = new Git(db)) {
  			git.commit().setMessage("initial commit").call();
  
  			assertStringArrayEquals("Already on 'master'",
  					execute("git checkout master"));
  		}
 	}
 
 	@Test
 	public void testCheckoutBranch() throws Exception {
 		try (Git git = new Git(db)) {
 			git.commit().setMessage("initial commit").call();
 			git.branchCreate().setName("side").call();
 
 			assertStringArrayEquals("Switched to branch 'side'",
 					execute("git checkout side"));
 		}
 	}
 
 	@Test
 	public void testCheckoutNewBranch() throws Exception {
 		try (Git git = new Git(db)) {
 			git.commit().setMessage("initial commit").call();
 
 			assertStringArrayEquals("Switched to a new branch 'side'",
 					execute("git checkout -b side"));
 		}
 	}
 
 	@Test
 	public void testCheckoutNonExistingBranch() throws Exception {
 		assertStringArrayEquals(
 				"error: pathspec 'side' did not match any file(s) known to git.",
 				executeExpectingException("git checkout side"));
 	}
 
 	@Test
 	public void testCheckoutNewBranchThatAlreadyExists() throws Exception {
 		try (Git git = new Git(db)) {
 			git.commit().setMessage("initial commit").call();
 
 			assertStringArrayEquals(
 					"fatal: A branch named 'master' already exists.",
 				executeUnchecked("git checkout -b master"));
 		}
 	}
 
 	@Test
 	public void testCheckoutNewBranchOnBranchToBeBorn() throws Exception {
 		assertStringArrayEquals("fatal: You are on a branch yet to be born",
 				executeUnchecked("git checkout -b side"));
 	}
 
 	@Test
 	public void testCheckoutUnresolvedHead() throws Exception {
 		assertStringArrayEquals(
 				"error: pathspec 'HEAD' did not match any file(s) known to git.",
 				executeExpectingException("git checkout HEAD"));
 	}
 
 	@Test
 	public void testCheckoutHead() throws Exception {
 		try (Git git = new Git(db)) {
 			git.commit().setMessage("initial commit").call();
 
 			assertStringArrayEquals("", execute("git checkout HEAD"));
 		}
 	}
 
 	@Test
 	public void testCheckoutExistingBranchWithConflict() throws Exception {
 		try (Git git = new Git(db)) {
 			writeTrashFile("a", "Hello world a");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("commit file a").call();
 			git.branchCreate().setName("branch_1").call();
 			git.rm().addFilepattern("a").call();
 			FileUtils.mkdirs(new File(db.getWorkTree(), "a"));
 			writeTrashFile("a/b", "Hello world b");
 			git.add().addFilepattern("a/b").call();
 			git.commit().setMessage("commit folder a").call();
 			git.rm().addFilepattern("a").call();
 			writeTrashFile("a", "New Hello world a");
 			git.add().addFilepattern(".").call();
 
 			String[] execute = executeExpectingException(
 					"git checkout branch_1");
 			assertEquals(
 					"error: Your local changes to the following files would be overwritten by checkout:",
 					execute[0]);
 			assertEquals("\ta", execute[1]);
 		}
 	}
 
 	/**
 	 * Steps:
 	 * <ol>
 	 * <li>Add file 'a' and 'b'
 	 * <li>Commit
 	 * <li>Create branch '1'
 	 * <li>modify file 'a'
 	 * <li>Commit
 	 * <li>Delete file 'a' in the working tree
 	 * <li>Checkout branch '1'
 	 * </ol>
 	 * <p>
 	 * The working tree should contain 'a' with FileMode.REGULAR_FILE after the
 	 * checkout.
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void testCheckoutWithMissingWorkingTreeFile() throws Exception {
 		try (Git git = new Git(db)) {
 			File fileA = writeTrashFile("a", "Hello world a");
 			writeTrashFile("b", "Hello world b");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("add files a & b").call();
 			Ref branch_1 = git.branchCreate().setName("branch_1").call();
 			writeTrashFile("a", "b");
 			git.add().addFilepattern("a").call();
 			git.commit().setMessage("modify file a").call();
 
 			FileEntry entry = new FileTreeIterator.FileEntry(new File(
 					db.getWorkTree(), "a"), db.getFS());
 			assertEquals(FileMode.REGULAR_FILE, entry.getMode());
 
 			FileUtils.delete(fileA);
 
 			git.checkout().setName(branch_1.getName()).call();
 
 			entry = new FileTreeIterator.FileEntry(new File(db.getWorkTree(), "a"),
 					db.getFS());
 			assertEquals(FileMode.REGULAR_FILE, entry.getMode());
 			assertEquals("Hello world a", read(fileA));
 		}
 	}
 
 	@Test
 	public void testCheckoutOrphan() throws Exception {
 		try (Git git = new Git(db)) {
 			git.commit().setMessage("initial commit").call();
 
 			assertStringArrayEquals("Switched to a new branch 'new_branch'",
 					execute("git checkout --orphan new_branch"));
 			assertEquals("refs/heads/new_branch",
 					db.exactRef("HEAD").getTarget().getName());
 			RevCommit commit = git.commit().setMessage("orphan commit").call();
 			assertEquals(0, commit.getParentCount());
 		}
 	}
 
 	/**
 	 * Steps:
 	 * <ol>
 	 * <li>Add file 'b'
 	 * <li>Commit
 	 * <li>Create branch '1'
 	 * <li>Add folder 'a'
 	 * <li>Commit
 	 * <li>Replace folder 'a' by file 'a' in the working tree
 	 * <li>Checkout branch '1'
 	 * </ol>
 	 * <p>
 	 * The checkout has to delete folder but the workingtree contains a dirty
 	 * file at this path. The checkout should fail like in native git.
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void fileModeTestMissingThenFolderWithFileInWorkingTree()
 			throws Exception {
 		try (Git git = new Git(db)) {
 			writeTrashFile("b", "Hello world b");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("add file b").call();
 			Ref branch_1 = git.branchCreate().setName("branch_1").call();
 			File folderA = new File(db.getWorkTree(), "a");
 			FileUtils.mkdirs(folderA);
 			writeTrashFile("a/c", "Hello world c");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("add folder a").call();
 
 			FileEntry entry = new FileTreeIterator.FileEntry(new File(
 					db.getWorkTree(), "a"), db.getFS());
 			assertEquals(FileMode.TREE, entry.getMode());
 
 			FileUtils.delete(folderA, FileUtils.RECURSIVE);
 			writeTrashFile("a", "b");
 
 			entry = new FileTreeIterator.FileEntry(new File(db.getWorkTree(), "a"),
 					db.getFS());
 			assertEquals(FileMode.REGULAR_FILE, entry.getMode());
 
 			try {
 				git.checkout().setName(branch_1.getName()).call();
 				fail("Don't get the expected conflict");
 			} catch (CheckoutConflictException e) {
 				assertEquals("[a]", e.getConflictingPaths().toString());
 				entry = new FileTreeIterator.FileEntry(
 						new File(db.getWorkTree(), "a"), db.getFS());
 				assertEquals(FileMode.REGULAR_FILE, entry.getMode());
 			}
 		}
 	}
 
 	/**
 	 * Steps:
 	 * <ol>
 	 * <li>Add file 'a'
 	 * <li>Commit
 	 * <li>Create branch '1'
 	 * <li>Replace file 'a' by folder 'a'
 	 * <li>Commit
 	 * <li>Delete folder 'a' in the working tree
 	 * <li>Checkout branch '1'
 	 * </ol>
 	 * <p>
 	 * The working tree should contain 'a' with FileMode.REGULAR_FILE after the
 	 * checkout.
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void fileModeTestFolderWithMissingInWorkingTree() throws Exception {
 		try (Git git = new Git(db)) {
 			writeTrashFile("b", "Hello world b");
 			writeTrashFile("a", "b");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("add file b & file a").call();
 			Ref branch_1 = git.branchCreate().setName("branch_1").call();
 			git.rm().addFilepattern("a").call();
 			File folderA = new File(db.getWorkTree(), "a");
 			FileUtils.mkdirs(folderA);
 			writeTrashFile("a/c", "Hello world c");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("add folder a").call();
 
 			FileEntry entry = new FileTreeIterator.FileEntry(new File(
 					db.getWorkTree(), "a"), db.getFS());
 			assertEquals(FileMode.TREE, entry.getMode());
 
 			FileUtils.delete(folderA, FileUtils.RECURSIVE);
 
 			git.checkout().setName(branch_1.getName()).call();
 
 			entry = new FileTreeIterator.FileEntry(new File(db.getWorkTree(), "a"),
 					db.getFS());
 			assertEquals(FileMode.REGULAR_FILE, entry.getMode());
 		}
 	}
 
 	/**
 	 * Steps:
 	 * <ol>
 	 * <li>Add file 'a'
 	 * <li>Commit
 	 * <li>Create branch '1'
 	 * <li>Delete file 'a'
 	 * <li>Commit
 	 * <li>Add folder 'a' in the working tree
 	 * <li>Checkout branch '1'
 	 * </ol>
 	 * <p>
 	 * The checkout command should raise an error. The conflicting paths are 'a'
 	 * and 'a/c'.
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void fileModeTestMissingWithFolderInWorkingTree() throws Exception {
 		try (Git git = new Git(db)) {
 			writeTrashFile("b", "Hello world b");
 			writeTrashFile("a", "b");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("add file b & file a").call();
 			Ref branch_1 = git.branchCreate().setName("branch_1").call();
 			git.rm().addFilepattern("a").call();
 			git.commit().setMessage("delete file a").call();
 
 			FileUtils.mkdirs(new File(db.getWorkTree(), "a"));
 			writeTrashFile("a/c", "Hello world c");
 
 			FileEntry entry = new FileTreeIterator.FileEntry(new File(
 					db.getWorkTree(), "a"), db.getFS());
 			assertEquals(FileMode.TREE, entry.getMode());
 
 			CheckoutConflictException exception = null;
 			try {
 				git.checkout().setName(branch_1.getName()).call();
 			} catch (CheckoutConflictException e) {
 				exception = e;
 			}
 			assertNotNull(exception);
 			assertEquals(2, exception.getConflictingPaths().size());
 			assertEquals("a", exception.getConflictingPaths().get(0));
 			assertEquals("a/c", exception.getConflictingPaths().get(1));
 		}
 	}
 
 	/**
 	 * Steps:
 	 * <ol>
 	 * <li>Add folder 'a'
 	 * <li>Commit
 	 * <li>Create branch '1'
 	 * <li>Delete folder 'a'
 	 * <li>Commit
 	 * <li>Add file 'a' in the working tree
 	 * <li>Checkout branch '1'
 	 * </ol>
 	 * <p>
 	 * The checkout command should raise an error. The conflicting path is 'a'.
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void fileModeTestFolderThenMissingWithFileInWorkingTree()
 			throws Exception {
 		try (Git git = new Git(db)) {
 			FileUtils.mkdirs(new File(db.getWorkTree(), "a"));
 			writeTrashFile("a/c", "Hello world c");
 			writeTrashFile("b", "Hello world b");
 			git.add().addFilepattern(".").call();
 			RevCommit commit1 = git.commit().setMessage("add folder a & file b")
 					.call();
 			Ref branch_1 = git.branchCreate().setName("branch_1").call();
 			git.rm().addFilepattern("a").call();
 			RevCommit commit2 = git.commit().setMessage("delete folder a").call();
 
 			TreeWalk tw = new TreeWalk(db);
 			tw.addTree(commit1.getTree());
 			tw.addTree(commit2.getTree());
 			List<DiffEntry> scan = DiffEntry.scan(tw);
 			assertEquals(1, scan.size());
 			assertEquals(FileMode.MISSING, scan.get(0).getNewMode());
 			assertEquals(FileMode.TREE, scan.get(0).getOldMode());
 
 			writeTrashFile("a", "b");
 
 			FileEntry entry = new FileTreeIterator.FileEntry(new File(
 					db.getWorkTree(), "a"), db.getFS());
 			assertEquals(FileMode.REGULAR_FILE, entry.getMode());
 
 			CheckoutConflictException exception = null;
 			try {
 				git.checkout().setName(branch_1.getName()).call();
 			} catch (CheckoutConflictException e) {
 				exception = e;
 			}
 			assertNotNull(exception);
 			assertEquals(1, exception.getConflictingPaths().size());
 			assertEquals("a", exception.getConflictingPaths().get(0));
 		}
 	}
 
 	/**
 	 * Steps:
 	 * <ol>
 	 * <li>Add folder 'a'
 	 * <li>Commit
 	 * <li>Create branch '1'
 	 * <li>Replace folder 'a'by file 'a'
 	 * <li>Commit
 	 * <li>Delete file 'a' in the working tree
 	 * <li>Checkout branch '1'
 	 * </ol>
 	 * <p>
 	 * The working tree should contain 'a' with FileMode.TREE after the
 	 * checkout.
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void fileModeTestFolderThenFileWithMissingInWorkingTree()
 			throws Exception {
 		try (Git git = new Git(db)) {
 			FileUtils.mkdirs(new File(db.getWorkTree(), "a"));
 			writeTrashFile("a/c", "Hello world c");
 			writeTrashFile("b", "Hello world b");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("add folder a & file b").call();
 			Ref branch_1 = git.branchCreate().setName("branch_1").call();
 			git.rm().addFilepattern("a").call();
 			File fileA = new File(db.getWorkTree(), "a");
 			writeTrashFile("a", "b");
 			git.add().addFilepattern("a").call();
 			git.commit().setMessage("add file a").call();
 
 			FileEntry entry = new FileTreeIterator.FileEntry(new File(
 					db.getWorkTree(), "a"), db.getFS());
 			assertEquals(FileMode.REGULAR_FILE, entry.getMode());
 
 			FileUtils.delete(fileA);
 
 			git.checkout().setName(branch_1.getName()).call();
 
 			entry = new FileTreeIterator.FileEntry(new File(db.getWorkTree(), "a"),
 					db.getFS());
 			assertEquals(FileMode.TREE, entry.getMode());
 		}
 	}
 
 	/**
 	 * Steps:
 	 * <ol>
 	 * <li>Add file 'a'
 	 * <li>Commit
 	 * <li>Create branch '1'
 	 * <li>Modify file 'a'
 	 * <li>Commit
 	 * <li>Delete file 'a' and replace by folder 'a' in the working tree and
 	 * index
 	 * <li>Checkout branch '1'
 	 * </ol>
 	 * <p>
 	 * The checkout command should raise an error. The conflicting path is 'a'.
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void fileModeTestFileThenFileWithFolderInIndex() throws Exception {
 		try (Git git = new Git(db)) {
 			writeTrashFile("a", "Hello world a");
 			writeTrashFile("b", "Hello world b");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("add files a & b").call();
 			Ref branch_1 = git.branchCreate().setName("branch_1").call();
 			writeTrashFile("a", "b");
 			git.add().addFilepattern("a").call();
 			git.commit().setMessage("add file a").call();
 
 			FileEntry entry = new FileTreeIterator.FileEntry(new File(
 					db.getWorkTree(), "a"), db.getFS());
 			assertEquals(FileMode.REGULAR_FILE, entry.getMode());
 
 			git.rm().addFilepattern("a").call();
 			FileUtils.mkdirs(new File(db.getWorkTree(), "a"));
 			writeTrashFile("a/c", "Hello world c");
 			git.add().addFilepattern(".").call();
 
 			entry = new FileTreeIterator.FileEntry(new File(db.getWorkTree(), "a"),
 					db.getFS());
 			assertEquals(FileMode.TREE, entry.getMode());
 
 			CheckoutConflictException exception = null;
 			try {
 				git.checkout().setName(branch_1.getName()).call();
 			} catch (CheckoutConflictException e) {
 				exception = e;
 			}
 			assertNotNull(exception);
 			assertEquals(1, exception.getConflictingPaths().size());
 			assertEquals("a", exception.getConflictingPaths().get(0));
 		}
 	}
 
 	/**
 	 * Steps:
 	 * <ol>
 	 * <li>Add file 'a'
 	 * <li>Commit
 	 * <li>Create branch '1'
 	 * <li>Modify file 'a'
 	 * <li>Commit
 	 * <li>Delete file 'a' and replace by folder 'a' in the working tree and
 	 * index
 	 * <li>Checkout branch '1'
 	 * </ol>
 	 * <p>
 	 * The checkout command should raise an error. The conflicting paths are 'a'
 	 * and 'a/c'.
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void fileModeTestFileWithFolderInIndex() throws Exception {
 		try (Git git = new Git(db)) {
 			writeTrashFile("b", "Hello world b");
 			writeTrashFile("a", "b");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("add file b & file a").call();
 			Ref branch_1 = git.branchCreate().setName("branch_1").call();
 			git.rm().addFilepattern("a").call();
 			writeTrashFile("a", "Hello world a");
 			git.add().addFilepattern("a").call();
 			git.commit().setMessage("add file a").call();
 
 			FileEntry entry = new FileTreeIterator.FileEntry(new File(
 					db.getWorkTree(), "a"), db.getFS());
 			assertEquals(FileMode.REGULAR_FILE, entry.getMode());
 
 			git.rm().addFilepattern("a").call();
 			FileUtils.mkdirs(new File(db.getWorkTree(), "a"));
 			writeTrashFile("a/c", "Hello world c");
 			git.add().addFilepattern(".").call();
 
 			entry = new FileTreeIterator.FileEntry(new File(db.getWorkTree(), "a"),
 					db.getFS());
 			assertEquals(FileMode.TREE, entry.getMode());
 
 			CheckoutConflictException exception = null;
 			try {
 				git.checkout().setName(branch_1.getName()).call();
 			} catch (CheckoutConflictException e) {
 				exception = e;
 			}
 			assertNotNull(exception);
 			assertEquals(1, exception.getConflictingPaths().size());
 			assertEquals("a", exception.getConflictingPaths().get(0));
 
 			// TODO: ideally we'd like to get two paths from this exception
 			// assertEquals(2, exception.getConflictingPaths().size());
 			// assertEquals("a", exception.getConflictingPaths().get(0));
 			// assertEquals("a/c", exception.getConflictingPaths().get(1));
 		}
 	}
 
 	@Test
 	public void testCheckoutPath() throws Exception {
 		try (Git git = new Git(db)) {
 			writeTrashFile("a", "Hello world a");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("commit file a").call();
 			git.branchCreate().setName("branch_1").call();
 			git.checkout().setName("branch_1").call();
 			File b = writeTrashFile("b", "Hello world b");
 			git.add().addFilepattern("b").call();
 			git.commit().setMessage("commit file b").call();
 			File a = writeTrashFile("a", "New Hello world a");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("modified a").call();
 			assertArrayEquals(new String[] { "" },
 					execute("git checkout HEAD~2 -- a"));
 			assertEquals("Hello world a", read(a));
 			assertArrayEquals(new String[] { "* branch_1", "  master", "" },
 					execute("git branch"));
 			assertEquals("Hello world b", read(b));
 		}
 	}
 
 	@Test
 	public void testCheckoutAllPaths() throws Exception {
 		try (Git git = new Git(db)) {
 			writeTrashFile("a", "Hello world a");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("commit file a").call();
 			git.branchCreate().setName("branch_1").call();
 			git.checkout().setName("branch_1").call();
 			File b = writeTrashFile("b", "Hello world b");
 			git.add().addFilepattern("b").call();
 			git.commit().setMessage("commit file b").call();
 			File a = writeTrashFile("a", "New Hello world a");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("modified a").call();
 			assertArrayEquals(new String[] { "" },
 					execute("git checkout HEAD~2 -- ."));
 			assertEquals("Hello world a", read(a));
 			assertArrayEquals(new String[] { "* branch_1", "  master", "" },
 					execute("git branch"));
 			assertEquals("Hello world b", read(b));
 		}
 	}
 
 	@Test
 	public void testCheckoutSingleFile() throws Exception {
 		try (Git git = new Git(db)) {
 			File a = writeTrashFile("a", "file a");
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("commit file a").call();
 			writeTrashFile("a", "b");
 			assertEquals("b", read(a));
 			assertEquals("[]", Arrays.toString(execute("git checkout -- a")));
 			assertEquals("file a", read(a));
 		}
 	}
 
 	@Test
 	public void testCheckoutLink() throws Exception {
 		Assume.assumeTrue(FS.DETECTED.supportsSymlinks());
 		try (Git git = new Git(db)) {
 			Path path = writeLink("a", "link_a");
 			assertTrue(Files.isSymbolicLink(path));
 			git.add().addFilepattern(".").call();
 			git.commit().setMessage("commit link a").call();
 			deleteTrashFile("a");
 			writeTrashFile("a", "Hello world a");
 			assertFalse(Files.isSymbolicLink(path));
 			assertEquals("[]", Arrays.toString(execute("git checkout -- a")));
 			assertEquals("link_a", FileUtils.readSymLink(path.toFile()));
 			assertTrue(Files.isSymbolicLink(path));
 		}
 	}
 }