Keep line endings for text files committed with CR/LF on text=auto

Git never converts line endings if the version in the repository is a
text file with CR/LF and text=auto. See [1]: "When the file has been
committed with CRLF, no conversion is done."

Because the sentence just before is about converting line endings on
check-in, I had understood that in commit 60cf85a [2] to mean that no
conversion on check-in was to be done. However, as bug 565048 and a
code inspection of the C git code showed it really means no conversion
is done on check-in *or check-out*.

If the text attribute is not set but core.autocrlf = true, this is
the same as text=auto eol=crlf. C git does not convert on check-out
even on text=auto eol=lf if the index version is a text file with
CR/LF.

For check-in, one has to look at the intended target, which is done
in WorkingTreeIterator since commit 60cf85a. For check-out, it can
be done by looking at the source and can thus be done in the
AutoLFOutputStream.

Additionally, provide a constructor for AutoLFInputStream to do
the same; for cases where the equivalent of a check-out is done via
an input stream obtained from a blob. (EGit does that in its
GitBlobStorage for the Eclipse compare framework; it's more efficient
than using a TemporaryBuffer and DirCacheCheckout.getContent(), and
it avoids the need for a temporary file.)

Adapt existing tests, and add new checkout and merge tests to verify
the resulting files have the correct line endings.

EGit's GitBlobStorage will need to call the new version of
EolStreamTypeUtil.wrapInputStream().

[1] https://git-scm.com/docs/gitattributes#Documentation/gitattributes.txt-Settostringvalueauto
[2] https://git.eclipse.org/r/c/jgit/jgit/+/127324

Bug: 565048
Change-Id: If1282ef43e2abd00263541bd10a01fe1f5c619fc
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>

5 files changed, 291 insertions, 117 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/EolStreamTypeUtilTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/EolStreamTypeUtilTest.java
index 1e3a39aad8..2a553ce1a2 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/EolStreamTypeUtilTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/EolStreamTypeUtilTest.java
@@ -1,43 +1,11 @@
 /*
- * Copyright (C) 2015, Ivan Motsch <ivan.motsch@bsiag.com>
+ * Copyright (C) 2015, 2020 Ivan Motsch <ivan.motsch@bsiag.com> and others
  *
- * 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
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://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.
+ * SPDX-License-Identifier: BSD-3-Clause
  */
 
 package org.eclipse.jgit.api;
@@ -90,16 +58,20 @@ public class EolStreamTypeUtilTest {
 		testCheckout(TEXT_LF, AUTO_LF, "\r", "\r");
 		testCheckout(TEXT_LF, AUTO_LF, "\n", "\n");
 
-		testCheckout(TEXT_LF, AUTO_LF, "\r\n", "\n");
+		testCheckout(TEXT_LF, null, "\r\n", "\n");
+		testCheckout(null, AUTO_LF, "\r\n", "\r\n");
 		testCheckout(TEXT_LF, AUTO_LF, "\n\r", "\n\r");
 
-		testCheckout(TEXT_LF, AUTO_LF, "\n\r\n", "\n\n");
-		testCheckout(TEXT_LF, AUTO_LF, "\r\n\r", "\n\r");
+		testCheckout(TEXT_LF, null, "\n\r\n", "\n\n");
+		testCheckout(null, AUTO_LF, "\n\r\n", "\n\r\n");
+		testCheckout(TEXT_LF, null, "\r\n\r", "\n\r");
+		testCheckout(null, AUTO_LF, "\r\n\r", "\r\n\r");
 
 		testCheckout(TEXT_LF, AUTO_LF, "a\nb\n", "a\nb\n");
 		testCheckout(TEXT_LF, AUTO_LF, "a\rb\r", "a\rb\r");
 		testCheckout(TEXT_LF, AUTO_LF, "a\n\rb\n\r", "a\n\rb\n\r");
-		testCheckout(TEXT_LF, AUTO_LF, "a\r\nb\r\n", "a\nb\n");
+		testCheckout(TEXT_LF, null, "a\r\nb\r\n", "a\nb\n");
+		testCheckout(null, AUTO_LF, "a\r\nb\r\n", "a\r\nb\r\n");
 	}
 
 	@Test
@@ -153,45 +125,49 @@ public class EolStreamTypeUtilTest {
 		byte[] outputBytes = output.getBytes(UTF_8);
 		byte[] expectedConversionBytes = expectedConversion.getBytes(UTF_8);
 
-		// test using output text and assuming it was declared TEXT
-		b = new ByteArrayOutputStream();
-		try (OutputStream out = EolStreamTypeUtil.wrapOutputStream(b,
-				streamTypeText)) {
-			out.write(outputBytes);
+		if (streamTypeText != null) {
+			// test using output text and assuming it was declared TEXT
+			b = new ByteArrayOutputStream();
+			try (OutputStream out = EolStreamTypeUtil.wrapOutputStream(b,
+					streamTypeText)) {
+				out.write(outputBytes);
+			}
+			assertArrayEquals(expectedConversionBytes, b.toByteArray());
 		}
-		assertArrayEquals(expectedConversionBytes, b.toByteArray());
-
-		// test using ouput text and assuming it was declared AUTO, using binary
-		// detection
-		b = new ByteArrayOutputStream();
-		try (OutputStream out = EolStreamTypeUtil.wrapOutputStream(b,
-				streamTypeWithBinaryCheck)) {
-			out.write(outputBytes);
+		if (streamTypeWithBinaryCheck != null) {
+			// test using output text and assuming it was declared AUTO, using
+			// binary detection
+			b = new ByteArrayOutputStream();
+			try (OutputStream out = EolStreamTypeUtil.wrapOutputStream(b,
+					streamTypeWithBinaryCheck)) {
+				out.write(outputBytes);
+			}
+			assertArrayEquals(expectedConversionBytes, b.toByteArray());
 		}
-		assertArrayEquals(expectedConversionBytes, b.toByteArray());
-
 		// now pollute output text with some binary bytes
 		outputBytes = extendWithBinaryData(outputBytes);
 		expectedConversionBytes = extendWithBinaryData(expectedConversionBytes);
 
-		// again, test using output text and assuming it was declared TEXT
-		b = new ByteArrayOutputStream();
-		try (OutputStream out = EolStreamTypeUtil.wrapOutputStream(b,
-				streamTypeText)) {
-			out.write(outputBytes);
+		if (streamTypeText != null) {
+			// again, test using output text and assuming it was declared TEXT
+			b = new ByteArrayOutputStream();
+			try (OutputStream out = EolStreamTypeUtil.wrapOutputStream(b,
+					streamTypeText)) {
+				out.write(outputBytes);
+			}
+			assertArrayEquals(expectedConversionBytes, b.toByteArray());
 		}
-		assertArrayEquals(expectedConversionBytes, b.toByteArray());
-
-		// again, test using ouput text and assuming it was declared AUTO, using
-		// binary
-		// detection
-		b = new ByteArrayOutputStream();
-		try (OutputStream out = EolStreamTypeUtil.wrapOutputStream(b,
-				streamTypeWithBinaryCheck)) {
-			out.write(outputBytes);
+		if (streamTypeWithBinaryCheck != null) {
+			// again, test using output text and assuming it was declared AUTO,
+			// using binary detection
+			b = new ByteArrayOutputStream();
+			try (OutputStream out = EolStreamTypeUtil.wrapOutputStream(b,
+					streamTypeWithBinaryCheck)) {
+				out.write(outputBytes);
+			}
+			// expect no conversion
+			assertArrayEquals(outputBytes, b.toByteArray());
 		}
-		// expect no conversion
-		assertArrayEquals(outputBytes, b.toByteArray());
 	}
 
 	@Test
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/DirCacheCheckoutTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/DirCacheCheckoutTest.java
index a272c8f2ee..b943486b1b 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/DirCacheCheckoutTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/DirCacheCheckoutTest.java
@@ -2,41 +2,13 @@
  * Copyright (C) 2007, Dave Watson <dwatson@mimvista.com>
  * Copyright (C) 2008-2011, Shawn O. Pearce <spearce@spearce.org>
  * Copyright (C) 2008-2011, Robin Rosenberg <robin.rosenberg@dewire.com>
- * Copyright (C) 2010-2011, Christian Halstrick <christian.halstrick@sap.com>
- * and other copyright owners as documented in the project's IP log.
+ * Copyright (C) 2010, 2020 Christian Halstrick <christian.halstrick@sap.com> and others
  *
  * 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
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://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.
+ * SPDX-License-Identifier: BSD-3-Clause
  */
 package org.eclipse.jgit.lib;
 
@@ -85,6 +57,7 @@ import org.eclipse.jgit.treewalk.TreeWalk;
 import org.eclipse.jgit.treewalk.WorkingTreeIterator;
 import org.eclipse.jgit.util.FS;
 import org.eclipse.jgit.util.FileUtils;
+import org.eclipse.jgit.util.StringUtils;
 import org.junit.Assume;
 import org.junit.Test;
 
@@ -284,6 +257,86 @@ public class DirCacheCheckoutTest extends RepositoryTestCase {
 		}
 	}
 
+	private void checkoutLineEndings(String inIndex, String expected,
+			String attributes) throws Exception {
+		try (Git git = new Git(db);
+				TestRepository<Repository> db_t = new TestRepository<>(db)) {
+			BranchBuilder master = db_t.branch("master");
+			master.commit().add("f", inIndex).message("m0").create();
+			if (!StringUtils.isEmptyOrNull(attributes)) {
+				master.commit().add(".gitattributes", attributes)
+						.message("attributes").create();
+			}
+			File f = new File(db.getWorkTree(), "f");
+			assertFalse(f.exists());
+			git.checkout().setName("master").call();
+			assertTrue(f.exists());
+			checkFile(f, expected);
+		}
+	}
+
+	@Test
+	public void testCheckoutWithCRLF() throws Exception {
+		checkoutLineEndings("first line\r\nsecond line\r\n",
+				"first line\r\nsecond line\r\n", null);
+	}
+
+	@Test
+	public void testCheckoutWithCRLFAuto() throws Exception {
+		checkoutLineEndings("first line\r\nsecond line\r\n",
+				"first line\r\nsecond line\r\n", "f text=auto");
+	}
+
+	@Test
+	public void testCheckoutWithCRLFAutoEolLf() throws Exception {
+		checkoutLineEndings("first line\r\nsecond line\r\n",
+				"first line\r\nsecond line\r\n", "f text=auto eol=lf");
+	}
+
+	@Test
+	public void testCheckoutWithCRLFAutoEolNative() throws Exception {
+		checkoutLineEndings("first line\r\nsecond line\r\n",
+				"first line\r\nsecond line\r\n", "f text=auto eol=native");
+	}
+
+	@Test
+	public void testCheckoutWithCRLFAutoEolCrLf() throws Exception {
+		checkoutLineEndings("first line\r\nsecond line\r\n",
+				"first line\r\nsecond line\r\n", "f text=auto eol=crlf");
+	}
+
+	@Test
+	public void testCheckoutWithLF() throws Exception {
+		checkoutLineEndings("first line\nsecond line\n",
+				"first line\nsecond line\n", null);
+	}
+
+	@Test
+	public void testCheckoutWithLFAuto() throws Exception {
+		checkoutLineEndings("first line\nsecond line\n",
+				"first line\nsecond line\n", "f text=auto");
+	}
+
+	@Test
+	public void testCheckoutWithLFAutoEolLf() throws Exception {
+		checkoutLineEndings("first line\nsecond line\n",
+				"first line\nsecond line\n", "f text=auto eol=lf");
+	}
+
+	@Test
+	public void testCheckoutWithLFAutoEolNative() throws Exception {
+		checkoutLineEndings(
+				"first line\nsecond line\n", "first line\nsecond line\n"
+						.replaceAll("\n", System.lineSeparator()),
+				"f text=auto eol=native");
+	}
+
+	@Test
+	public void testCheckoutWithLFAutoEolCrLf() throws Exception {
+		checkoutLineEndings("first line\nsecond line\n",
+				"first line\r\nsecond line\r\n", "f text=auto eol=crlf");
+	}
+
 	private DirCacheCheckout resetHard(RevCommit commit)
 			throws NoWorkTreeException,
 			CorruptObjectException, IOException {
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/MergerTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/MergerTest.java
index 7a244e1d8b..e2ac89be90 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/MergerTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/MergerTest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2012, Robin Stocker <robin@nibor.org> and others
+ * Copyright (C) 2012, 2020 Robin Stocker <robin@nibor.org> and others
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Distribution License v. 1.0 which is available at
@@ -367,6 +367,48 @@ public class MergerTest extends RepositoryTestCase {
 	}
 
 	@Theory
+	public void mergeConflictWithCrLfTextAuto(MergeStrategy strategy)
+			throws IOException, GitAPIException {
+		Git git = Git.wrap(db);
+		writeTrashFile("crlf.txt", "a crlf file\r\n");
+		git.add().addFilepattern("crlf.txt").call();
+		git.commit().setMessage("base").call();
+		assertEquals("[crlf.txt, mode:100644, content:a crlf file\r\n]",
+				indexState(CONTENT));
+		writeTrashFile(".gitattributes", "crlf.txt text=auto");
+		git.add().addFilepattern(".gitattributes").call();
+		git.commit().setMessage("attributes").call();
+
+		git.branchCreate().setName("brancha").call();
+
+		writeTrashFile("crlf.txt", "a crlf file\r\na second line\r\n");
+		git.add().addFilepattern("crlf.txt").call();
+		git.commit().setMessage("on master").call();
+		assertEquals(
+				"[.gitattributes, mode:100644, content:crlf.txt text=auto]"
+						+ "[crlf.txt, mode:100644, content:a crlf file\r\na second line\r\n]",
+				indexState(CONTENT));
+
+		git.checkout().setName("brancha").call();
+		File testFile = writeTrashFile("crlf.txt",
+				"a crlf file\r\nanother line\r\n");
+		git.add().addFilepattern("crlf.txt").call();
+		git.commit().setMessage("on brancha").call();
+
+		MergeResult mergeResult = git.merge().setStrategy(strategy)
+				.include(db.resolve("master")).call();
+		assertEquals(MergeResult.MergeStatus.CONFLICTING,
+				mergeResult.getMergeStatus());
+		checkFile(testFile,
+				"a crlf file\r\n" //
+						+ "<<<<<<< HEAD\n" //
+						+ "another line\r\n" //
+						+ "=======\n" //
+						+ "a second line\r\n" //
+						+ ">>>>>>> 8e9e704742f1bc8a41eac88aac4aeefd338b7384\n");
+	}
+
+	@Theory
 	public void mergeWithCrlfAutoCrlfTrue(MergeStrategy strategy)
 			throws IOException, GitAPIException {
 		Git git = Git.wrap(db);
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/io/AutoLFInputStreamTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/io/AutoLFInputStreamTest.java
index fb90461e1a..c391694fbc 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/io/AutoLFInputStreamTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/io/AutoLFInputStreamTest.java
@@ -1,6 +1,6 @@
 /*
  * Copyright (C) 2010, Marc Strapetz <marc.strapetz@syntevo.com>
- * Copyright (C) 2015, Ivan Motsch <ivan.motsch@bsiag.com> and others
+ * Copyright (C) 2015, 2020 Ivan Motsch <ivan.motsch@bsiag.com> and others
  *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Distribution License v. 1.0 which is available at
@@ -17,7 +17,9 @@ import static org.junit.Assert.assertEquals;
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.util.function.Function;
 
+import org.eclipse.jgit.util.io.AutoLFInputStream.StreamFlag;
 import org.junit.Test;
 
 public class AutoLFInputStreamTest {
@@ -25,47 +27,65 @@ public class AutoLFInputStreamTest {
 	@Test
 	public void testLF() throws IOException {
 		final byte[] bytes = asBytes("1\n2\n3");
-		test(bytes, bytes, false);
+		test(bytes, bytes);
 	}
 
 	@Test
 	public void testCR() throws IOException {
 		final byte[] bytes = asBytes("1\r2\r3");
-		test(bytes, bytes, false);
+		test(bytes, bytes);
 	}
 
 	@Test
 	public void testCRLF() throws IOException {
-		test(asBytes("1\r\n2\r\n3"), asBytes("1\n2\n3"), false);
+		test(asBytes("1\r\n2\r\n3"), asBytes("1\n2\n3"));
 	}
 
 	@Test
 	public void testLFCR() throws IOException {
 		final byte[] bytes = asBytes("1\n\r2\n\r3");
-		test(bytes, bytes, false);
+		test(bytes, bytes);
 	}
 
 	@Test
 	public void testEmpty() throws IOException {
 		final byte[] bytes = asBytes("");
-		test(bytes, bytes, false);
+		test(bytes, bytes);
 	}
 
 	@Test
 	public void testBinaryDetect() throws IOException {
 		final byte[] bytes = asBytes("1\r\n2\r\n3\0");
-		test(bytes, bytes, true);
+		test(bytes, bytes, StreamFlag.DETECT_BINARY);
 	}
 
 	@Test
 	public void testBinaryDontDetect() throws IOException {
-		test(asBytes("1\r\n2\r\n3\0"), asBytes("1\n2\n3\0"), false);
+		test(asBytes("1\r\n2\r\n3\0"), asBytes("1\n2\n3\0"));
+	}
+
+	@Test
+	public void testCrLf() throws IOException {
+		byte[] bytes = asBytes("1\r\n2\n3\r\n\r");
+		test(bytes, bytes, in -> AutoLFInputStream.create(in,
+				StreamFlag.DETECT_BINARY, StreamFlag.FOR_CHECKOUT));
+	}
+
+	@Test
+	public void testCrLfDontDetect() throws IOException {
+		test(asBytes("1\r\n2\r\n"), asBytes("1\n2\n"),
+				in -> AutoLFInputStream.create(in, StreamFlag.DETECT_BINARY));
+	}
+
+	private static void test(byte[] input, byte[] expected, StreamFlag... flags)
+			throws IOException {
+		test(input, expected, in -> AutoLFInputStream.create(in, flags));
 	}
 
 	private static void test(byte[] input, byte[] expected,
-			boolean detectBinary) throws IOException {
+			Function<InputStream, InputStream> factory) throws IOException {
 		try (InputStream bis1 = new ByteArrayInputStream(input);
-				InputStream cis1 = new AutoLFInputStream(bis1, detectBinary)) {
+				InputStream cis1 = factory.apply(bis1)) {
 			int index1 = 0;
 			for (int b = cis1.read(); b != -1; b = cis1.read()) {
 				assertEquals(expected[index1], (byte) b);
@@ -77,8 +97,7 @@ public class AutoLFInputStreamTest {
 			for (int bufferSize = 1; bufferSize < 10; bufferSize++) {
 				final byte[] buffer = new byte[bufferSize];
 				try (InputStream bis2 = new ByteArrayInputStream(input);
-						InputStream cis2 = new AutoLFInputStream(bis2,
-								detectBinary)) {
+						InputStream cis2 = factory.apply(bis2)) {
 
 					int read = 0;
 					for (int readNow = cis2.read(buffer, 0,
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/io/AutoLFOutputStreamTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/io/AutoLFOutputStreamTest.java
new file mode 100644
index 0000000000..1b7e55e457
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/util/io/AutoLFOutputStreamTest.java
@@ -0,0 +1,84 @@
+/*
+ * Copyright (C) 2020, Thomas Wolf <thomas.wolf@paranor.ch> and others
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * https://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+package org.eclipse.jgit.util.io;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.junit.Assert.assertArrayEquals;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+
+import org.junit.Test;
+
+public class AutoLFOutputStreamTest {
+
+	@Test
+	public void testLF() throws IOException {
+		final byte[] bytes = asBytes("1\n2\n3");
+		test(bytes, bytes, false);
+	}
+
+	@Test
+	public void testCR() throws IOException {
+		final byte[] bytes = asBytes("1\r2\r3");
+		test(bytes, bytes, false);
+	}
+
+	@Test
+	public void testCRLFNoDetect() throws IOException {
+		test(asBytes("1\r\n2\r\n3"), asBytes("1\n2\n3"), false);
+	}
+
+	@Test
+	public void testLFCR() throws IOException {
+		final byte[] bytes = asBytes("1\n\r2\n\r3");
+		test(bytes, bytes, false);
+	}
+
+	@Test
+	public void testEmpty() throws IOException {
+		final byte[] bytes = asBytes("");
+		test(bytes, bytes, false);
+	}
+
+	@Test
+	public void testBinaryDetect() throws IOException {
+		final byte[] bytes = asBytes("1\r\n2\r\n3\0");
+		test(bytes, bytes, true);
+	}
+
+	@Test
+	public void testBinaryDontDetect() throws IOException {
+		test(asBytes("1\r\n2\r\n3\0"), asBytes("1\n2\n3\0"), false);
+	}
+
+	@Test
+	public void testCrLfDetect() throws IOException {
+		byte[] bytes = asBytes("1\r\n2\n3\r\n\r");
+		test(bytes, bytes, true);
+	}
+
+	private static void test(byte[] input, byte[] expected,
+			boolean detectBinary) throws IOException {
+		try (ByteArrayOutputStream result = new ByteArrayOutputStream();
+				OutputStream out = new AutoLFOutputStream(result,
+						detectBinary)) {
+			out.write(input);
+			out.close();
+			assertArrayEquals(expected, result.toByteArray());
+		}
+	}
+
+	private static byte[] asBytes(String in) {
+		return in.getBytes(UTF_8);
+	}
+}