/*
    * Copyright (C) 2012 Google Inc.
    * 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 java.nio.charset.StandardCharsets.UTF_8;
  import static org.junit.Assert.assertArrayEquals;
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.fail;
  import static org.junit.Assume.assumeNoException;
  
  import java.io.BufferedInputStream;
  import java.io.BufferedReader;
  import java.io.ByteArrayInputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.FileOutputStream;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.OutputStream;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  import java.util.concurrent.ExecutorService;
  import java.util.concurrent.Executors;
  import java.util.concurrent.Future;
  import java.util.zip.ZipEntry;
  import java.util.zip.ZipInputStream;
  
  import org.eclipse.jgit.api.Git;
  import org.eclipse.jgit.dircache.DirCache;
  import org.eclipse.jgit.lib.CLIRepositoryTestCase;
  import org.eclipse.jgit.lib.FileMode;
  import org.junit.Before;
  import org.junit.Test;
  
  public class ArchiveTest extends CLIRepositoryTestCase {
  	private Git git;
  	private String emptyTree;
  
  	@Override
  	@Before
  	public void setUp() throws Exception {
  		super.setUp();
  		git = new Git(db);
  		git.commit().setMessage("initial commit").call();
  		emptyTree = db.resolve("HEAD^{tree}").abbreviate(12).name();
  	}
  
  	@Test
  	public void testEmptyArchive() throws Exception {
  		byte[] result = CLIGitCommand.executeRaw(
  				"git archive --format=zip " + emptyTree, db).outBytes();
  		assertArrayEquals(new String[0], listZipEntries(result));
  	}
  
  	@Test
  	public void testEmptyTar() throws Exception {
  		byte[] result = CLIGitCommand.executeRaw(
  				"git archive --format=tar " + emptyTree, db).outBytes();
 		assertArrayEquals(new String[0], listTarEntries(result));
 	}
 
 	@Test
 	public void testUnrecognizedFormat() throws Exception {
 		String[] expect = new String[] {
 				"fatal: Unknown archive format 'nonsense'", "" };
 		String[] actual = executeUnchecked(
 				"git archive --format=nonsense " + emptyTree);
 		assertArrayEquals(expect, actual);
 	}
 
 	@Test
 	public void testArchiveWithFiles() throws Exception {
 		writeTrashFile("a", "a file with content!");
 		writeTrashFile("c", ""); // empty file
 		writeTrashFile("unrelated", "another file, just for kicks");
 		git.add().addFilepattern("a").call();
 		git.add().addFilepattern("c").call();
 		git.commit().setMessage("populate toplevel").call();
 
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --format=zip HEAD", db).outBytes();
 		assertArrayEquals(new String[] { "a", "c" },
 				listZipEntries(result));
 	}
 
 	private void commitGreeting() throws Exception {
 		writeTrashFile("greeting", "hello, world!");
 		git.add().addFilepattern("greeting").call();
 		git.commit().setMessage("a commit with a file").call();
 	}
 
 	@Test
 	public void testDefaultFormatIsTar() throws Exception {
 		commitGreeting();
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive HEAD", db).outBytes();
 		assertArrayEquals(new String[] { "greeting" },
 				listTarEntries(result));
 	}
 
 	private static String shellQuote(String s) {
 		return "'" + s.replace("'", "'\\''") + "'";
 	}
 
 	@Test
 	public void testFormatOverridesFilename() throws Exception {
 		File archive = new File(db.getWorkTree(), "format-overrides-name.tar");
 		String path = archive.getAbsolutePath();
 
 		commitGreeting();
 		assertArrayEquals(new String[] { "" },
 				execute("git archive " +
 					"--format=zip " +
 					shellQuote("--output=" + path) + " " +
 					"HEAD"));
 		assertContainsEntryWithMode(path, "", "greeting");
 		assertIsZip(archive);
 	}
 
 	@Test
 	public void testUnrecognizedExtensionMeansTar() throws Exception {
 		File archive = new File(db.getWorkTree(), "example.txt");
 		String path = archive.getAbsolutePath();
 
 		commitGreeting();
 		assertArrayEquals(new String[] { "" },
 				execute("git archive " +
 					shellQuote("--output=" + path) + " " +
 					"HEAD"));
 		assertTarContainsEntry(path, "", "greeting");
 		assertIsTar(archive);
 	}
 
 	@Test
 	public void testNoExtensionMeansTar() throws Exception {
 		File archive = new File(db.getWorkTree(), "example");
 		String path = archive.getAbsolutePath();
 
 		commitGreeting();
 		assertArrayEquals(new String[] { "" },
 				execute("git archive " +
 					shellQuote("--output=" + path) + " " +
 					"HEAD"));
 		assertIsTar(archive);
 	}
 
 	@Test
 	public void testExtensionMatchIsAnchored() throws Exception {
 		File archive = new File(db.getWorkTree(), "two-extensions.zip.bak");
 		String path = archive.getAbsolutePath();
 
 		commitGreeting();
 		assertArrayEquals(new String[] { "" },
 				execute("git archive " +
 					shellQuote("--output=" + path) + " " +
 					"HEAD"));
 		assertIsTar(archive);
 	}
 
 	@Test
 	public void testZipExtension() throws Exception {
 		File archiveWithDot = new File(db.getWorkTree(), "greeting.zip");
 		File archiveNoDot = new File(db.getWorkTree(), "greetingzip");
 
 		commitGreeting();
 		execute("git archive " +
 			shellQuote("--output=" + archiveWithDot.getAbsolutePath()) + " " +
 			"HEAD");
 		execute("git archive " +
 			shellQuote("--output=" + archiveNoDot.getAbsolutePath()) + " " +
 			"HEAD");
 		assertIsZip(archiveWithDot);
 		assertIsTar(archiveNoDot);
 	}
 
 	@Test
 	public void testTarExtension() throws Exception {
 		File archive = new File(db.getWorkTree(), "tarball.tar");
 		String path = archive.getAbsolutePath();
 
 		commitGreeting();
 		assertArrayEquals(new String[] { "" },
 				execute("git archive " +
 					shellQuote("--output=" + path) + " " +
 					"HEAD"));
 		assertIsTar(archive);
 	}
 
 	@Test
 	public void testTgzExtensions() throws Exception {
 		commitGreeting();
 
 		for (String ext : Arrays.asList("tar.gz", "tgz")) {
 			File archiveWithDot = new File(db.getWorkTree(), "tarball." + ext);
 			File archiveNoDot = new File(db.getWorkTree(), "tarball" + ext);
 
 			execute("git archive " +
 				shellQuote("--output=" + archiveWithDot.getAbsolutePath()) + " " +
 				"HEAD");
 			execute("git archive " +
 				shellQuote("--output=" + archiveNoDot.getAbsolutePath()) + " " +
 				"HEAD");
 			assertIsGzip(archiveWithDot);
 			assertIsTar(archiveNoDot);
 		}
 	}
 
 	@Test
 	public void testTbz2Extension() throws Exception {
 		commitGreeting();
 
 		for (String ext : Arrays.asList("tar.bz2", "tbz", "tbz2")) {
 			File archiveWithDot = new File(db.getWorkTree(), "tarball." + ext);
 			File archiveNoDot = new File(db.getWorkTree(), "tarball" + ext);
 
 			execute("git archive " +
 				shellQuote("--output=" + archiveWithDot.getAbsolutePath()) + " " +
 				"HEAD");
 			execute("git archive " +
 				shellQuote("--output=" + archiveNoDot.getAbsolutePath()) + " " +
 				"HEAD");
 			assertIsBzip2(archiveWithDot);
 			assertIsTar(archiveNoDot);
 		}
 	}
 
 	@Test
 	public void testTxzExtension() throws Exception {
 		commitGreeting();
 
 		for (String ext : Arrays.asList("tar.xz", "txz")) {
 			File archiveWithDot = new File(db.getWorkTree(), "tarball." + ext);
 			File archiveNoDot = new File(db.getWorkTree(), "tarball" + ext);
 
 			execute("git archive " +
 				shellQuote("--output=" + archiveWithDot.getAbsolutePath()) + " " +
 				"HEAD");
 			execute("git archive " +
 				shellQuote("--output=" + archiveNoDot.getAbsolutePath()) + " " +
 				"HEAD");
 			assertIsXz(archiveWithDot);
 			assertIsTar(archiveNoDot);
 		}
 	}
 
 	@Test
 	public void testArchiveWithSubdir() throws Exception {
 		writeTrashFile("a", "a file with content!");
 		writeTrashFile("b.c", "before subdir in git sort order");
 		writeTrashFile("b0c", "after subdir in git sort order");
 		writeTrashFile("c", "");
 		git.add().addFilepattern("a").call();
 		git.add().addFilepattern("b.c").call();
 		git.add().addFilepattern("b0c").call();
 		git.add().addFilepattern("c").call();
 		git.commit().setMessage("populate toplevel").call();
 		writeTrashFile("b/b", "file in subdirectory");
 		writeTrashFile("b/a", "another file in subdirectory");
 		git.add().addFilepattern("b").call();
 		git.commit().setMessage("add subdir").call();
 
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --format=zip master", db).outBytes();
 		String[] expect = { "a", "b.c", "b0c", "b/", "b/a", "b/b", "c" };
 		String[] actual = listZipEntries(result);
 
 		Arrays.sort(expect);
 		Arrays.sort(actual);
 		assertArrayEquals(expect, actual);
 	}
 
 	@Test
 	public void testTarWithSubdir() throws Exception {
 		writeTrashFile("a", "a file with content!");
 		writeTrashFile("b.c", "before subdir in git sort order");
 		writeTrashFile("b0c", "after subdir in git sort order");
 		writeTrashFile("c", "");
 		git.add().addFilepattern("a").call();
 		git.add().addFilepattern("b.c").call();
 		git.add().addFilepattern("b0c").call();
 		git.add().addFilepattern("c").call();
 		git.commit().setMessage("populate toplevel").call();
 		writeTrashFile("b/b", "file in subdirectory");
 		writeTrashFile("b/a", "another file in subdirectory");
 		git.add().addFilepattern("b").call();
 		git.commit().setMessage("add subdir").call();
 
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --format=tar master", db).outBytes();
 		String[] expect = { "a", "b.c", "b0c", "b/", "b/a", "b/b", "c" };
 		String[] actual = listTarEntries(result);
 
 		Arrays.sort(expect);
 		Arrays.sort(actual);
 		assertArrayEquals(expect, actual);
 	}
 
 	private void commitBazAndFooSlashBar() throws Exception {
 		writeTrashFile("baz", "a file");
 		writeTrashFile("foo/bar", "another file");
 		git.add().addFilepattern("baz").call();
 		git.add().addFilepattern("foo").call();
 		git.commit().setMessage("sample commit").call();
 	}
 
 	@Test
 	public void testArchivePrefixOption() throws Exception {
 		commitBazAndFooSlashBar();
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --prefix=x/ --format=zip master", db).outBytes();
 		String[] expect = { "x/", "x/baz", "x/foo/", "x/foo/bar" };
 		String[] actual = listZipEntries(result);
 
 		Arrays.sort(expect);
 		Arrays.sort(actual);
 		assertArrayEquals(expect, actual);
 	}
 
 	@Test
 	public void testTarPrefixOption() throws Exception {
 		commitBazAndFooSlashBar();
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --prefix=x/ --format=tar master", db).outBytes();
 		String[] expect = { "x/", "x/baz", "x/foo/", "x/foo/bar" };
 		String[] actual = listTarEntries(result);
 
 		Arrays.sort(expect);
 		Arrays.sort(actual);
 		assertArrayEquals(expect, actual);
 	}
 
 	private void commitFoo() throws Exception {
 		writeTrashFile("foo", "a file");
 		git.add().addFilepattern("foo").call();
 		git.commit().setMessage("boring commit").call();
 	}
 
 	@Test
 	public void testPrefixDoesNotNormalizeDoubleSlash() throws Exception {
 		commitFoo();
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --prefix=x// --format=zip master", db).outBytes();
 		String[] expect = { "x/", "x//foo" };
 		assertArrayEquals(expect, listZipEntries(result));
 	}
 
 	@Test
 	public void testPrefixDoesNotNormalizeDoubleSlashInTar() throws Exception {
 		commitFoo();
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --prefix=x// --format=tar master", db).outBytes();
 		String[] expect = { "x/", "x//foo" };
 		assertArrayEquals(expect, listTarEntries(result));
 	}
 
 	/**
 	 * The prefix passed to "git archive" need not end with '/'.
 	 * In practice it is not very common to have a nonempty prefix
 	 * that does not name a directory (and hence end with /), but
 	 * since git has historically supported other prefixes, we do,
 	 * too.
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void testPrefixWithoutTrailingSlash() throws Exception {
 		commitBazAndFooSlashBar();
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --prefix=my- --format=zip master", db).outBytes();
 		String[] expect = { "my-baz", "my-foo/", "my-foo/bar" };
 		String[] actual = listZipEntries(result);
 
 		Arrays.sort(expect);
 		Arrays.sort(actual);
 		assertArrayEquals(expect, actual);
 	}
 
 	@Test
 	public void testTarPrefixWithoutTrailingSlash() throws Exception {
 		commitBazAndFooSlashBar();
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --prefix=my- --format=tar master", db).outBytes();
 		String[] expect = { "my-baz", "my-foo/", "my-foo/bar" };
 		String[] actual = listTarEntries(result);
 
 		Arrays.sort(expect);
 		Arrays.sort(actual);
 		assertArrayEquals(expect, actual);
 	}
 
 	@Test
 	public void testArchiveIncludesSubmoduleDirectory() throws Exception {
 		writeTrashFile("a", "a file with content!");
 		writeTrashFile("c", "after submodule");
 		git.add().addFilepattern("a").call();
 		git.add().addFilepattern("c").call();
 		git.commit().setMessage("initial commit").call();
 		git.submoduleAdd().setURI("./.").setPath("b").call().close();
 		git.commit().setMessage("add submodule").call();
 
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --format=zip master", db).outBytes();
 		String[] expect = { ".gitmodules", "a", "b/", "c" };
 		String[] actual = listZipEntries(result);
 
 		Arrays.sort(expect);
 		Arrays.sort(actual);
 		assertArrayEquals(expect, actual);
 	}
 
 	@Test
 	public void testTarIncludesSubmoduleDirectory() throws Exception {
 		writeTrashFile("a", "a file with content!");
 		writeTrashFile("c", "after submodule");
 		git.add().addFilepattern("a").call();
 		git.add().addFilepattern("c").call();
 		git.commit().setMessage("initial commit").call();
 		git.submoduleAdd().setURI("./.").setPath("b").call().close();
 		git.commit().setMessage("add submodule").call();
 
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --format=tar master", db).outBytes();
 		String[] expect = { ".gitmodules", "a", "b/", "c" };
 		String[] actual = listTarEntries(result);
 
 		Arrays.sort(expect);
 		Arrays.sort(actual);
 		assertArrayEquals(expect, actual);
 	}
 
 	@Test
 	public void testArchivePreservesMode() throws Exception {
 		writeTrashFile("plain", "a file with content");
 		writeTrashFile("executable", "an executable file");
 		writeTrashFile("symlink", "plain");
 		writeTrashFile("dir/content", "clutter in a subdir");
 		git.add().addFilepattern("plain").call();
 		git.add().addFilepattern("executable").call();
 		git.add().addFilepattern("symlink").call();
 		git.add().addFilepattern("dir").call();
 
 		DirCache cache = db.lockDirCache();
 		cache.getEntry("executable").setFileMode(FileMode.EXECUTABLE_FILE);
 		cache.getEntry("symlink").setFileMode(FileMode.SYMLINK);
 		cache.write();
 		cache.commit();
 		cache.unlock();
 
 		git.commit().setMessage("three files with different modes").call();
 
 		byte[] zipData = CLIGitCommand.executeRaw(
 				"git archive --format=zip master", db).outBytes();
 		writeRaw("zip-with-modes.zip", zipData);
 		assertContainsEntryWithMode("zip-with-modes.zip", "-rw-", "plain");
 		assertContainsEntryWithMode("zip-with-modes.zip", "-rwx", "executable");
 		assertContainsEntryWithMode("zip-with-modes.zip", "l", "symlink");
 		assertContainsEntryWithMode("zip-with-modes.zip", "-rw-", "dir/");
 	}
 
 	@Test
 	public void testTarPreservesMode() throws Exception {
 		writeTrashFile("plain", "a file with content");
 		writeTrashFile("executable", "an executable file");
 		writeTrashFile("symlink", "plain");
 		writeTrashFile("dir/content", "clutter in a subdir");
 		git.add().addFilepattern("plain").call();
 		git.add().addFilepattern("executable").call();
 		git.add().addFilepattern("symlink").call();
 		git.add().addFilepattern("dir").call();
 
 		DirCache cache = db.lockDirCache();
 		cache.getEntry("executable").setFileMode(FileMode.EXECUTABLE_FILE);
 		cache.getEntry("symlink").setFileMode(FileMode.SYMLINK);
 		cache.write();
 		cache.commit();
 		cache.unlock();
 
 		git.commit().setMessage("three files with different modes").call();
 
 		byte[] archive = CLIGitCommand.executeRaw(
 				"git archive --format=tar master", db).outBytes();
 		writeRaw("with-modes.tar", archive);
 		assertTarContainsEntry("with-modes.tar", "-rw-r--r--", "plain");
 		assertTarContainsEntry("with-modes.tar", "-rwxr-xr-x", "executable");
 		assertTarContainsEntry("with-modes.tar", "l", "symlink -> plain");
 		assertTarContainsEntry("with-modes.tar", "drwxr-xr-x", "dir/");
 	}
 
 	@Test
 	public void testArchiveWithLongFilename() throws Exception {
 		StringBuilder filename = new StringBuilder();
 		List<String> l = new ArrayList<>();
 		for (int i = 0; i < 20; i++) {
 			filename.append("1234567890/");
 			l.add(filename.toString());
 		}
 		filename.append("1234567890");
 		l.add(filename.toString());
 		writeTrashFile(filename.toString(), "file with long path");
 		git.add().addFilepattern("1234567890").call();
 		git.commit().setMessage("file with long name").call();
 
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --format=zip HEAD", db).outBytes();
 		assertArrayEquals(l.toArray(new String[0]),
 				listZipEntries(result));
 	}
 
 	@Test
 	public void testTarWithLongFilename() throws Exception {
 		StringBuilder filename = new StringBuilder();
 		List<String> l = new ArrayList<>();
 		for (int i = 0; i < 20; i++) {
 			filename.append("1234567890/");
 			l.add(filename.toString());
 		}
 		filename.append("1234567890");
 		l.add(filename.toString());
 		writeTrashFile(filename.toString(), "file with long path");
 		git.add().addFilepattern("1234567890").call();
 		git.commit().setMessage("file with long name").call();
 
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --format=tar HEAD", db).outBytes();
 		assertArrayEquals(l.toArray(new String[0]),
 				listTarEntries(result));
 	}
 
 	@Test
 	public void testArchivePreservesContent() throws Exception {
 		String payload = "“The quick brown fox jumps over the lazy dog!”";
 		writeTrashFile("xyzzy", payload);
 		git.add().addFilepattern("xyzzy").call();
 		git.commit().setMessage("add file with content").call();
 
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --format=zip HEAD", db).outBytes();
 		assertArrayEquals(new String[] { payload },
 				zipEntryContent(result, "xyzzy"));
 	}
 
 	@Test
 	public void testTarPreservesContent() throws Exception {
 		String payload = "“The quick brown fox jumps over the lazy dog!”";
 		writeTrashFile("xyzzy", payload);
 		git.add().addFilepattern("xyzzy").call();
 		git.commit().setMessage("add file with content").call();
 
 		byte[] result = CLIGitCommand.executeRaw(
 				"git archive --format=tar HEAD", db).outBytes();
 		assertArrayEquals(new String[] { payload },
 				tarEntryContent(result, "xyzzy"));
 	}
 
 	private Process spawnAssumingCommandPresent(String... cmdline) {
 		File cwd = db.getWorkTree();
 		ProcessBuilder procBuilder = new ProcessBuilder(cmdline)
 				.directory(cwd)
 				.redirectErrorStream(true);
 		Process proc = null;
 		try {
 			proc = procBuilder.start();
 		} catch (IOException e) {
 			// On machines without `cmdline[0]`, let the test pass.
 			assumeNoException(e);
 		}
 
 		return proc;
 	}
 
 	private BufferedReader readFromProcess(Process proc) throws Exception {
 		return new BufferedReader(
 				new InputStreamReader(proc.getInputStream(), UTF_8));
 	}
 
 	private void grepForEntry(String name, String mode, String... cmdline)
 			throws Exception {
 		Process proc = spawnAssumingCommandPresent(cmdline);
 		proc.getOutputStream().close();
 		BufferedReader reader = readFromProcess(proc);
 		try {
 			String line;
 			while ((line = reader.readLine()) != null)
 				if (line.startsWith(mode) && line.endsWith(name))
 					// found it!
 					return;
 			fail("expected entry " + name + " with mode " + mode + " but found none");
 		} finally {
 			proc.getOutputStream().close();
 			proc.destroy();
 		}
 	}
 
 	private void assertMagic(long offset, byte[] magicBytes, File file) throws Exception {
 		try (BufferedInputStream in = new BufferedInputStream(
 				new FileInputStream(file))) {
 			if (offset > 0) {
 				long skipped = in.skip(offset);
 				assertEquals(offset, skipped);
 			}
 
 			byte[] actual = new byte[magicBytes.length];
 			in.read(actual);
 			assertArrayEquals(magicBytes, actual);
 		}
 	}
 
 	private void assertMagic(byte[] magicBytes, File file) throws Exception {
 		assertMagic(0, magicBytes, file);
 	}
 
 	private void assertIsTar(File file) throws Exception {
 		assertMagic(257, new byte[] { 'u', 's', 't', 'a', 'r', 0 }, file);
 	}
 
 	private void assertIsZip(File file) throws Exception {
 		assertMagic(new byte[] { 'P', 'K', 3, 4 }, file);
 	}
 
 	private void assertIsGzip(File file) throws Exception {
 		assertMagic(new byte[] { 037, (byte) 0213 }, file);
 	}
 
 	private void assertIsBzip2(File file) throws Exception {
 		assertMagic(new byte[] { 'B', 'Z', 'h' }, file);
 	}
 
 	private void assertIsXz(File file) throws Exception {
 		assertMagic(new byte[] { (byte) 0xfd, '7', 'z', 'X', 'Z', 0 }, file);
 	}
 
 	private void assertContainsEntryWithMode(String zipFilename, String mode, String name)
 			throws Exception {
 		grepForEntry(name, mode, "zipinfo", zipFilename);
 	}
 
 	private void assertTarContainsEntry(String tarfile, String mode, String name)
 			throws Exception {
 		grepForEntry(name, mode, "tar", "tvf", tarfile);
 	}
 
 	private void writeRaw(String filename, byte[] data)
 			throws IOException {
 		File path = new File(db.getWorkTree(), filename);
 		try (OutputStream out = new FileOutputStream(path)) {
 			out.write(data);
 		}
 	}
 
 	private static String[] listZipEntries(byte[] zipData) throws IOException {
 		List<String> l = new ArrayList<>();
 		try (ZipInputStream in = new ZipInputStream(
 				new ByteArrayInputStream(zipData))) {
 			ZipEntry e;
 			while ((e = in.getNextEntry()) != null)
 				l.add(e.getName());
 		}
 		return l.toArray(new String[0]);
 	}
 
 	private static Future<Object> writeAsync(OutputStream stream, byte[] data) {
 		ExecutorService executor = Executors.newSingleThreadExecutor();
 
 		return executor.submit(() -> {
 			try {
 				stream.write(data);
 				return null;
 			} finally {
 				stream.close();
 			}
 		});
 	}
 
 	private String[] listTarEntries(byte[] tarData) throws Exception {
 		List<String> l = new ArrayList<>();
 		Process proc = spawnAssumingCommandPresent("tar", "tf", "-");
 		try (BufferedReader reader = readFromProcess(proc)) {
 			OutputStream out = proc.getOutputStream();
 
 			// Dump tarball to tar stdin in background
 			Future<?> writing = writeAsync(out, tarData);
 
 			try {
 				String line;
 				while ((line = reader.readLine()) != null)
 					l.add(line);
 
 				return l.toArray(new String[0]);
 			} finally {
 				writing.get();
 				proc.destroy();
 			}
 		}
 	}
 
 	private static String[] zipEntryContent(byte[] zipData, String path)
 			throws IOException {
 		ZipInputStream in = new ZipInputStream(
 				new ByteArrayInputStream(zipData));
 		ZipEntry e;
 		while ((e = in.getNextEntry()) != null) {
 			if (!e.getName().equals(path))
 				continue;
 
 			// found!
 			List<String> l = new ArrayList<>();
 			BufferedReader reader = new BufferedReader(
 					new InputStreamReader(in, UTF_8));
 			String line;
 			while ((line = reader.readLine()) != null)
 				l.add(line);
 			return l.toArray(new String[0]);
 		}
 
 		// not found
 		return null;
 	}
 
 	private String[] tarEntryContent(byte[] tarData, String path)
 			throws Exception {
 		List<String> l = new ArrayList<>();
 		Process proc = spawnAssumingCommandPresent("tar", "Oxf", "-", path);
 		try (BufferedReader reader = readFromProcess(proc)) {
 			OutputStream out = proc.getOutputStream();
 			Future<?> writing = writeAsync(out, tarData);
 
 			try {
 				String line;
 				while ((line = reader.readLine()) != null)
 					l.add(line);
 
 				return l.toArray(new String[0]);
 			} finally {
 				writing.get();
 				proc.destroy();
 			}
 		}
 	}
 }