org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/ObjectDirectoryTest.java - jgit - Git at Google

 /*
  * Copyright (C) 2012, Roberto Tyley <roberto.tyley@gmail.com>
  *
  * 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.internal.storage.file;

 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;

 import java.io.File;
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.text.MessageFormat;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Set;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.Future;

 import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.junit.RepositoryTestCase;
 import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.revwalk.RevCommit;
 import org.eclipse.jgit.storage.file.FileBasedConfig;
 import org.eclipse.jgit.util.FS;
 import org.junit.Assume;
 import org.junit.Test;
 import org.mockito.Mockito;

 public class ObjectDirectoryTest extends RepositoryTestCase {

 	@Test
 	public void testConcurrentInsertionOfBlobsToTheSameNewFanOutDirectory()
 			throws Exception {
 		ExecutorService e = Executors.newCachedThreadPool();
 		for (int i=0; i < 100; ++i) {
 			ObjectDirectory dir = createBareRepository().getObjectDatabase();
 			for (Future f : e.invokeAll(blobInsertersForTheSameFanOutDir(dir))) {
 				f.get();
 			}
 		}
 	}

 	/**
 	 * Test packfile scanning while a gc is done from the outside (different
 	 * process or different Repository instance). This situation occurs e.g. if
 	 * a gerrit server is serving fetch requests while native git is doing a
 	 * garbage collection. The test shows that when core.trustfolderstat==true
 	 * jgit may miss to detect that a new packfile was created. This situation
 	 * is persistent until a new full rescan of the pack directory is triggered.
 	 *
 	 * The test works with two Repository instances working on the same disk
 	 * location. One (db) for all write operations (creating commits, doing gc)
 	 * and another one (receivingDB) which just reads and which in the end shows
 	 * the bug
 	 *
 	 * @throws Exception
 	 */
 	@Test
 	public void testScanningForPackfiles() throws Exception {
 		ObjectId unknownID = ObjectId
 				.fromString("c0ffee09d0b63d694bf49bc1e6847473f42d4a8c");
 		GC gc = new GC(db);
 		gc.setExpireAgeMillis(0);
 		gc.setPackExpireAgeMillis(0);

 		// the default repo db is used to create the objects. The receivingDB
 		// repo is used to trigger gc's
 		try (FileRepository receivingDB = new FileRepository(
 				db.getDirectory())) {
 			// set trustfolderstat to true. If set to false the test always
 			// succeeds.
 			FileBasedConfig cfg = receivingDB.getConfig();
 			cfg.setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
 					ConfigConstants.CONFIG_KEY_TRUSTFOLDERSTAT, true);
 			cfg.save();

 			// setup a repo which has at least one pack file and trigger
 			// scanning of the packs directory
 			ObjectId id = commitFile("file.txt", "test", "master").getId();
 			gc.gc().get();
 			assertFalse(receivingDB.getObjectDatabase().has(unknownID));
 			assertTrue(receivingDB.getObjectDatabase().hasPackedObject(id));

 			// preparations
 			File packsFolder = receivingDB.getObjectDatabase()
 					.getPackDirectory();
 			// prepare creation of a temporary file in the pack folder. This
 			// simulates that a native git gc is happening starting to write
 			// temporary files but has not yet finished
 			File tmpFile = new File(packsFolder, "1.tmp");
 			RevCommit id2 = commitFile("file.txt", "test2", "master");
 			// wait until filesystem timer ticks. This raises probability that
 			// the next statements are executed in the same tick as the
 			// filesystem timer
 			fsTick(null);

 			// create a Temp file in the packs folder and trigger a rescan of
 			// the packs folder. This lets receivingDB think it has scanned the
 			// packs folder at the current fs timestamp t1. The following gc
 			// will create new files which have the same timestamp t1 but this
 			// will not update the mtime of the packs folder. Because of that
 			// JGit will not rescan the packs folder later on and fails to see
 			// the pack file created during gc.
 			assertTrue(tmpFile.createNewFile());
 			assertFalse(receivingDB.getObjectDatabase().has(unknownID));

 			// trigger a gc. This will create packfiles which have likely the
 			// same mtime than the packfolder
 			gc.gc().get();

 			// To deal with racy-git situations JGit's Filesnapshot class will
 			// report a file/folder potentially dirty if
 			// cachedLastReadTime-cachedLastModificationTime < filesystem
 			// timestamp resolution. This causes JGit to always rescan a file
 			// after modification. But: this was true only if the difference
 			// between current system time and cachedLastModification time was
 			// less than 2500ms. If the modification is more than 2500ms ago we
 			// may have reported a file/folder to be clean although it has not
 			// been rescanned. A bug. To show the bug we sleep for more than
 			// 2500ms
 			Thread.sleep(2600);

 			File[] ret = packsFolder.listFiles(
 					(File dir, String name) -> name.endsWith(".pack"));
 			assertTrue(ret != null && ret.length == 1);
 			FS fs = db.getFS();
 			Assume.assumeTrue(fs.lastModifiedInstant(tmpFile)
 					.equals(fs.lastModifiedInstant(ret[0])));

 			// all objects are in a new packfile but we will not detect it
 			assertFalse(receivingDB.getObjectDatabase().has(unknownID));
 			assertTrue(receivingDB.getObjectDatabase().has(id2));
 		}
 	}

 	@Test
 	public void testShallowFile()
 			throws Exception {
 		FileRepository repository = createBareRepository();
 		ObjectDirectory dir = repository.getObjectDatabase();

 		String commit = "d3148f9410b071edd4a4c85d2a43d1fa2574b0d2";
 		try (PrintWriter writer = new PrintWriter(
 				new File(repository.getDirectory(), Constants.SHALLOW),
 				UTF_8.name())) {
 			writer.println(commit);
 		}
 		Set<ObjectId> shallowCommits = dir.getShallowCommits();
 		assertTrue(shallowCommits.remove(ObjectId.fromString(commit)));
 		assertTrue(shallowCommits.isEmpty());
 	}

 	@Test
 	public void testOpenLooseObjectSuppressStaleFileHandleException()
 			throws Exception {
 		ObjectId id = ObjectId
 				.fromString("873fb8d667d05436d728c52b1d7a09528e6eb59b");
 		WindowCursor curs = new WindowCursor(db.getObjectDatabase());

 		LooseObjects mock = mock(LooseObjects.class);
 		UnpackedObjectCache unpackedObjectCacheMock = mock(
 				UnpackedObjectCache.class);

 		Mockito.when(mock.getObjectLoader(any(), any(), any()))
 				.thenThrow(new IOException("Stale File Handle"));
 		Mockito.when(mock.open(curs, id)).thenCallRealMethod();
 		Mockito.when(mock.unpackedObjectCache())
 				.thenReturn(unpackedObjectCacheMock);

 		assertNull(mock.open(curs, id));
 		verify(unpackedObjectCacheMock).remove(id);
 	}

 	@Test
 	public void testOpenLooseObjectPropagatesIOExceptions() throws Exception {
 		ObjectId id = ObjectId
 				.fromString("873fb8d667d05436d728c52b1d7a09528e6eb59b");
 		WindowCursor curs = new WindowCursor(db.getObjectDatabase());

 		LooseObjects mock = mock(LooseObjects.class);

 		Mockito.when(mock.getObjectLoader(any(), any(), any()))
 				.thenThrow(new IOException("some IO failure"));
 		Mockito.when(mock.open(curs, id)).thenCallRealMethod();

 		assertThrows(IOException.class, () -> mock.open(curs, id));
 	}

 	@Test
 	public void testWindowCursorGetCommitGraph() throws Exception {
 		db.getConfig().setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
 				ConfigConstants.CONFIG_COMMIT_GRAPH, true);
 		db.getConfig().setBoolean(ConfigConstants.CONFIG_GC_SECTION, null,
 				ConfigConstants.CONFIG_KEY_WRITE_COMMIT_GRAPH, true);

 		WindowCursor curs = new WindowCursor(db.getObjectDatabase());
 		assertTrue(curs.getCommitGraph().isEmpty());
 		commitFile("file.txt", "content", "master");
 		GC gc = new GC(db);
 		gc.gc().get();
 		assertTrue(curs.getCommitGraph().isPresent());

 		db.getConfig().setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
 				ConfigConstants.CONFIG_COMMIT_GRAPH, false);

 		assertTrue(curs.getCommitGraph().isEmpty());
 	}

 	@Test
 	public void testShallowFileCorrupt() throws Exception {
 		FileRepository repository = createBareRepository();
 		ObjectDirectory dir = repository.getObjectDatabase();

 		String commit = "X3148f9410b071edd4a4c85d2a43d1fa2574b0d2";
 		try (PrintWriter writer = new PrintWriter(
 				new File(repository.getDirectory(), Constants.SHALLOW),
 				UTF_8.name())) {
 			writer.println(commit);
 		}
 		assertThrows(
 				MessageFormat.format(JGitText.get().badShallowLine, commit),
 				IOException.class, () -> dir.getShallowCommits());
 	}

 	@Test
 	public void testGetCommitGraph() throws Exception {
 		db.getConfig().setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
 				ConfigConstants.CONFIG_COMMIT_GRAPH, true);
 		db.getConfig().setBoolean(ConfigConstants.CONFIG_GC_SECTION, null,
 				ConfigConstants.CONFIG_KEY_WRITE_COMMIT_GRAPH, true);

 		// no commit-graph
 		ObjectDirectory dir = db.getObjectDatabase();
 		assertTrue(dir.getCommitGraph().isEmpty());

 		// add commit-graph
 		commitFile("file.txt", "content", "master");
 		GC gc = new GC(db);
 		gc.gc().get();
 		File file = new File(db.getObjectsDirectory(),
 				Constants.INFO_COMMIT_GRAPH);
 		assertTrue(file.exists());
 		assertTrue(file.isFile());
 		assertTrue(dir.getCommitGraph().isPresent());
 		assertEquals(1, dir.getCommitGraph().get().getCommitCnt());

 		// update commit-graph
 		commitFile("file2.txt", "content", "master");
 		gc.gc().get();
 		assertEquals(2, dir.getCommitGraph().get().getCommitCnt());

 		// delete commit-graph
 		file.delete();
 		assertFalse(file.exists());
 		assertTrue(dir.getCommitGraph().isEmpty());

 		// commit-graph is corrupt
 		try (PrintWriter writer = new PrintWriter(file, UTF_8.name())) {
 			writer.println("this is a corrupt commit-graph");
 		}
 		assertTrue(dir.getCommitGraph().isEmpty());

 		// add commit-graph again
 		gc.gc().get();
 		assertTrue(dir.getCommitGraph().isPresent());
 		assertEquals(2, dir.getCommitGraph().get().getCommitCnt());
 	}

 	private Collection<Callable<ObjectId>> blobInsertersForTheSameFanOutDir(
 			final ObjectDirectory dir) {
 		Callable<ObjectId> callable = () -> dir.newInserter()
 				.insert(Constants.OBJ_BLOB, new byte[0]);
 		return Collections.nCopies(4, callable);
 	}

 }
	/*
	* Copyright (C) 2012, Roberto Tyley <roberto.tyley@gmail.com>
	*
	* 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.internal.storage.file;

	import static java.nio.charset.StandardCharsets.UTF_8;
	import static org.junit.Assert.assertEquals;
	import static org.junit.Assert.assertFalse;
	import static org.junit.Assert.assertNull;
	import static org.junit.Assert.assertThrows;
	import static org.junit.Assert.assertTrue;
	import static org.mockito.ArgumentMatchers.any;
	import static org.mockito.Mockito.mock;
	import static org.mockito.Mockito.verify;

	import java.io.File;
	import java.io.IOException;
	import java.io.PrintWriter;
	import java.text.MessageFormat;
	import java.util.Collection;
	import java.util.Collections;
	import java.util.Set;
	import java.util.concurrent.Callable;
	import java.util.concurrent.ExecutorService;
	import java.util.concurrent.Executors;
	import java.util.concurrent.Future;

	import org.eclipse.jgit.internal.JGitText;
	import org.eclipse.jgit.junit.RepositoryTestCase;
	import org.eclipse.jgit.lib.ConfigConstants;
	import org.eclipse.jgit.lib.Constants;
	import org.eclipse.jgit.lib.ObjectId;
	import org.eclipse.jgit.revwalk.RevCommit;
	import org.eclipse.jgit.storage.file.FileBasedConfig;
	import org.eclipse.jgit.util.FS;
	import org.junit.Assume;
	import org.junit.Test;
	import org.mockito.Mockito;

	public class ObjectDirectoryTest extends RepositoryTestCase {

	@Test
	public void testConcurrentInsertionOfBlobsToTheSameNewFanOutDirectory()
	throws Exception {
	ExecutorService e = Executors.newCachedThreadPool();
	for (int i=0; i < 100; ++i) {
	ObjectDirectory dir = createBareRepository().getObjectDatabase();
	for (Future f : e.invokeAll(blobInsertersForTheSameFanOutDir(dir))) {
	f.get();
	}
	}
	}

	/**
	* Test packfile scanning while a gc is done from the outside (different
	* process or different Repository instance). This situation occurs e.g. if
	* a gerrit server is serving fetch requests while native git is doing a
	* garbage collection. The test shows that when core.trustfolderstat==true
	* jgit may miss to detect that a new packfile was created. This situation
	* is persistent until a new full rescan of the pack directory is triggered.
	*
	* The test works with two Repository instances working on the same disk
	* location. One (db) for all write operations (creating commits, doing gc)
	* and another one (receivingDB) which just reads and which in the end shows
	* the bug
	*
	* @throws Exception
	*/
	@Test
	public void testScanningForPackfiles() throws Exception {
	ObjectId unknownID = ObjectId
	.fromString("c0ffee09d0b63d694bf49bc1e6847473f42d4a8c");
	GC gc = new GC(db);
	gc.setExpireAgeMillis(0);
	gc.setPackExpireAgeMillis(0);

	// the default repo db is used to create the objects. The receivingDB
	// repo is used to trigger gc's
	try (FileRepository receivingDB = new FileRepository(
	db.getDirectory())) {
	// set trustfolderstat to true. If set to false the test always
	// succeeds.
	FileBasedConfig cfg = receivingDB.getConfig();
	cfg.setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
	ConfigConstants.CONFIG_KEY_TRUSTFOLDERSTAT, true);
	cfg.save();

	// setup a repo which has at least one pack file and trigger
	// scanning of the packs directory
	ObjectId id = commitFile("file.txt", "test", "master").getId();
	gc.gc().get();
	assertFalse(receivingDB.getObjectDatabase().has(unknownID));
	assertTrue(receivingDB.getObjectDatabase().hasPackedObject(id));

	// preparations
	File packsFolder = receivingDB.getObjectDatabase()
	.getPackDirectory();
	// prepare creation of a temporary file in the pack folder. This
	// simulates that a native git gc is happening starting to write
	// temporary files but has not yet finished
	File tmpFile = new File(packsFolder, "1.tmp");
	RevCommit id2 = commitFile("file.txt", "test2", "master");
	// wait until filesystem timer ticks. This raises probability that
	// the next statements are executed in the same tick as the
	// filesystem timer
	fsTick(null);

	// create a Temp file in the packs folder and trigger a rescan of
	// the packs folder. This lets receivingDB think it has scanned the
	// packs folder at the current fs timestamp t1. The following gc
	// will create new files which have the same timestamp t1 but this
	// will not update the mtime of the packs folder. Because of that
	// JGit will not rescan the packs folder later on and fails to see
	// the pack file created during gc.
	assertTrue(tmpFile.createNewFile());
	assertFalse(receivingDB.getObjectDatabase().has(unknownID));

	// trigger a gc. This will create packfiles which have likely the
	// same mtime than the packfolder
	gc.gc().get();

	// To deal with racy-git situations JGit's Filesnapshot class will
	// report a file/folder potentially dirty if
	// cachedLastReadTime-cachedLastModificationTime < filesystem
	// timestamp resolution. This causes JGit to always rescan a file
	// after modification. But: this was true only if the difference
	// between current system time and cachedLastModification time was
	// less than 2500ms. If the modification is more than 2500ms ago we
	// may have reported a file/folder to be clean although it has not
	// been rescanned. A bug. To show the bug we sleep for more than
	// 2500ms
	Thread.sleep(2600);

	File[] ret = packsFolder.listFiles(
	(File dir, String name) -> name.endsWith(".pack"));
	assertTrue(ret != null && ret.length == 1);
	FS fs = db.getFS();
	Assume.assumeTrue(fs.lastModifiedInstant(tmpFile)
	.equals(fs.lastModifiedInstant(ret[0])));

	// all objects are in a new packfile but we will not detect it
	assertFalse(receivingDB.getObjectDatabase().has(unknownID));
	assertTrue(receivingDB.getObjectDatabase().has(id2));
	}
	}

	@Test
	public void testShallowFile()
	throws Exception {
	FileRepository repository = createBareRepository();
	ObjectDirectory dir = repository.getObjectDatabase();

	String commit = "d3148f9410b071edd4a4c85d2a43d1fa2574b0d2";
	try (PrintWriter writer = new PrintWriter(
	new File(repository.getDirectory(), Constants.SHALLOW),
	UTF_8.name())) {
	writer.println(commit);
	}
	Set<ObjectId> shallowCommits = dir.getShallowCommits();
	assertTrue(shallowCommits.remove(ObjectId.fromString(commit)));
	assertTrue(shallowCommits.isEmpty());
	}

	@Test
	public void testOpenLooseObjectSuppressStaleFileHandleException()
	throws Exception {
	ObjectId id = ObjectId
	.fromString("873fb8d667d05436d728c52b1d7a09528e6eb59b");
	WindowCursor curs = new WindowCursor(db.getObjectDatabase());

	LooseObjects mock = mock(LooseObjects.class);
	UnpackedObjectCache unpackedObjectCacheMock = mock(
	UnpackedObjectCache.class);

	Mockito.when(mock.getObjectLoader(any(), any(), any()))
	.thenThrow(new IOException("Stale File Handle"));
	Mockito.when(mock.open(curs, id)).thenCallRealMethod();
	Mockito.when(mock.unpackedObjectCache())
	.thenReturn(unpackedObjectCacheMock);

	assertNull(mock.open(curs, id));
	verify(unpackedObjectCacheMock).remove(id);
	}

	@Test
	public void testOpenLooseObjectPropagatesIOExceptions() throws Exception {
	ObjectId id = ObjectId
	.fromString("873fb8d667d05436d728c52b1d7a09528e6eb59b");
	WindowCursor curs = new WindowCursor(db.getObjectDatabase());

	LooseObjects mock = mock(LooseObjects.class);

	Mockito.when(mock.getObjectLoader(any(), any(), any()))
	.thenThrow(new IOException("some IO failure"));
	Mockito.when(mock.open(curs, id)).thenCallRealMethod();

	assertThrows(IOException.class, () -> mock.open(curs, id));
	}

	@Test
	public void testWindowCursorGetCommitGraph() throws Exception {
	db.getConfig().setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
	ConfigConstants.CONFIG_COMMIT_GRAPH, true);
	db.getConfig().setBoolean(ConfigConstants.CONFIG_GC_SECTION, null,
	ConfigConstants.CONFIG_KEY_WRITE_COMMIT_GRAPH, true);

	WindowCursor curs = new WindowCursor(db.getObjectDatabase());
	assertTrue(curs.getCommitGraph().isEmpty());
	commitFile("file.txt", "content", "master");
	GC gc = new GC(db);
	gc.gc().get();
	assertTrue(curs.getCommitGraph().isPresent());

	db.getConfig().setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
	ConfigConstants.CONFIG_COMMIT_GRAPH, false);

	assertTrue(curs.getCommitGraph().isEmpty());
	}

	@Test
	public void testShallowFileCorrupt() throws Exception {
	FileRepository repository = createBareRepository();
	ObjectDirectory dir = repository.getObjectDatabase();

	String commit = "X3148f9410b071edd4a4c85d2a43d1fa2574b0d2";
	try (PrintWriter writer = new PrintWriter(
	new File(repository.getDirectory(), Constants.SHALLOW),
	UTF_8.name())) {
	writer.println(commit);
	}
	assertThrows(
	MessageFormat.format(JGitText.get().badShallowLine, commit),
	IOException.class, () -> dir.getShallowCommits());
	}

	@Test
	public void testGetCommitGraph() throws Exception {
	db.getConfig().setBoolean(ConfigConstants.CONFIG_CORE_SECTION, null,
	ConfigConstants.CONFIG_COMMIT_GRAPH, true);
	db.getConfig().setBoolean(ConfigConstants.CONFIG_GC_SECTION, null,
	ConfigConstants.CONFIG_KEY_WRITE_COMMIT_GRAPH, true);

	// no commit-graph
	ObjectDirectory dir = db.getObjectDatabase();
	assertTrue(dir.getCommitGraph().isEmpty());

	// add commit-graph
	commitFile("file.txt", "content", "master");
	GC gc = new GC(db);
	gc.gc().get();
	File file = new File(db.getObjectsDirectory(),
	Constants.INFO_COMMIT_GRAPH);
	assertTrue(file.exists());
	assertTrue(file.isFile());
	assertTrue(dir.getCommitGraph().isPresent());
	assertEquals(1, dir.getCommitGraph().get().getCommitCnt());

	// update commit-graph
	commitFile("file2.txt", "content", "master");
	gc.gc().get();
	assertEquals(2, dir.getCommitGraph().get().getCommitCnt());

	// delete commit-graph
	file.delete();
	assertFalse(file.exists());
	assertTrue(dir.getCommitGraph().isEmpty());

	// commit-graph is corrupt
	try (PrintWriter writer = new PrintWriter(file, UTF_8.name())) {
	writer.println("this is a corrupt commit-graph");
	}
	assertTrue(dir.getCommitGraph().isEmpty());

	// add commit-graph again
	gc.gc().get();
	assertTrue(dir.getCommitGraph().isPresent());
	assertEquals(2, dir.getCommitGraph().get().getCommitCnt());
	}

	private Collection<Callable<ObjectId>> blobInsertersForTheSameFanOutDir(
	final ObjectDirectory dir) {
	Callable<ObjectId> callable = () -> dir.newInserter()
	.insert(Constants.OBJ_BLOB, new byte[0]);
	return Collections.nCopies(4, callable);
	}

	}