diff --git a/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/BouncyCastleGpgSigner.java b/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/BouncyCastleGpgSigner.java
index ea159c5..449c4a4 100644
--- a/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/BouncyCastleGpgSigner.java
+++ b/org.eclipse.jgit.gpg.bc/src/org/eclipse/jgit/gpg/bc/internal/BouncyCastleGpgSigner.java
@@ -38,6 +38,8 @@
 import org.eclipse.jgit.lib.CommitBuilder;
 import org.eclipse.jgit.lib.GpgSignature;
 import org.eclipse.jgit.lib.GpgSigner;
+import org.eclipse.jgit.lib.GpgObjectSigner;
+import org.eclipse.jgit.lib.ObjectBuilder;
 import org.eclipse.jgit.lib.PersonIdent;
 import org.eclipse.jgit.transport.CredentialsProvider;
 import org.eclipse.jgit.util.StringUtils;
@@ -45,7 +47,8 @@
 /**
  * GPG Signer using BouncyCastle library
  */
-public class BouncyCastleGpgSigner extends GpgSigner {
+public class BouncyCastleGpgSigner extends GpgSigner
+		implements GpgObjectSigner {
 
 	private static void registerBouncyCastleProviderIfNecessary() {
 		if (Security.getProvider(BouncyCastleProvider.PROVIDER_NAME) == null) {
@@ -98,6 +101,13 @@
 	public void sign(@NonNull CommitBuilder commit,
 			@Nullable String gpgSigningKey, @NonNull PersonIdent committer,
 			CredentialsProvider credentialsProvider) throws CanceledException {
+		signObject(commit, gpgSigningKey, committer, credentialsProvider);
+	}
+
+	@Override
+	public void signObject(@NonNull ObjectBuilder object,
+			@Nullable String gpgSigningKey, @NonNull PersonIdent committer,
+			CredentialsProvider credentialsProvider) throws CanceledException {
 		try (BouncyCastleGpgKeyPassphrasePrompt passphrasePrompt = new BouncyCastleGpgKeyPassphrasePrompt(
 				credentialsProvider)) {
 			BouncyCastleGpgKey gpgKey = locateSigningKey(gpgSigningKey,
@@ -158,10 +168,10 @@
 			ByteArrayOutputStream buffer = new ByteArrayOutputStream();
 			try (BCPGOutputStream out = new BCPGOutputStream(
 					new ArmoredOutputStream(buffer))) {
-				signatureGenerator.update(commit.build());
+				signatureGenerator.update(object.build());
 				signatureGenerator.generate().encode(out);
 			}
-			commit.setGpgSignature(new GpgSignature(buffer.toByteArray()));
+			object.setGpgSignature(new GpgSignature(buffer.toByteArray()));
 		} catch (PGPException | IOException | NoSuchAlgorithmException
 				| NoSuchProviderException | URISyntaxException e) {
 			throw new JGitInternalException(e.getMessage(), e);
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/CommitBuilderTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/CommitBuilderTest.java
index dee58f9..2f1bada 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/CommitBuilderTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/CommitBuilderTest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2018, Salesforce. and others
+ * Copyright (C) 2018, 2020 Salesforce. 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
@@ -53,7 +53,7 @@
 	private void assertGpgSignatureStringOutcome(String signature,
 			String expectedOutcome) throws IOException {
 		ByteArrayOutputStream out = new ByteArrayOutputStream();
-		CommitBuilder.writeGpgSignatureString(signature, out);
+		ObjectBuilder.writeMultiLineHeader(signature, out, true);
 		String formatted_signature = new String(out.toByteArray(), US_ASCII);
 		assertEquals(expectedOutcome, formatted_signature);
 	}
@@ -85,8 +85,8 @@
 		String signature = "Ü Ä";
 		IllegalArgumentException e = assertThrows(
 				IllegalArgumentException.class,
-				() -> CommitBuilder.writeGpgSignatureString(signature,
-						new ByteArrayOutputStream()));
+				() -> ObjectBuilder.writeMultiLineHeader(signature,
+						new ByteArrayOutputStream(), true));
 		String message = MessageFormat.format(JGitText.get().notASCIIString,
 				signature);
 		assertEquals(message, e.getMessage());
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/TagBuilderTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/TagBuilderTest.java
new file mode 100644
index 0000000..5786022
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/TagBuilderTest.java
@@ -0,0 +1,173 @@
+/*
+ * 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.lib;
+
+import static java.nio.charset.StandardCharsets.US_ASCII;
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
+
+import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.util.RawParseUtils;
+import org.junit.Test;
+
+public class TagBuilderTest {
+
+	// @formatter:off
+	private static final String SIGNATURE = "-----BEGIN PGP SIGNATURE-----\n" +
+			"Version: BCPG v1.60\n" +
+			"\n" +
+			"iQEcBAABCAAGBQJb9cVhAAoJEKX+6Axg/6TZeFsH/0CY0WX/z7U8+7S5giFX4wH4\n" +
+			"opvBwqyt6OX8lgNwTwBGHFNt8LdmDCCmKoq/XwkNi3ARVjLhe3gBcKXNoavvPk2Z\n" +
+			"gIg5ChevGkU4afWCOMLVEYnkCBGw2+86XhrK1P7gTHEk1Rd+Yv1ZRDJBY+fFO7yz\n" +
+			"uSBuF5RpEY2sJiIvp27Gub/rY3B5NTR/feO/z+b9oiP/fMUhpRwG5KuWUsn9NPjw\n" +
+			"3tvbgawYpU/2UnS+xnavMY4t2fjRYjsoxndPLb2MUX8X7vC7FgWLBlmI/rquLZVM\n" +
+			"IQEKkjnA+lhejjK1rv+ulq4kGZJFKGYWYYhRDwFg5PTkzhudhN2SGUq5Wxq1Eg4=\n" +
+			"=b9OI\n" +
+			"-----END PGP SIGNATURE-----";
+
+	// @formatter:on
+
+	private static final String TAGGER_LINE = "A U. Thor <a_u_thor@example.com> 1218123387 +0700";
+
+	private static final PersonIdent TAGGER = RawParseUtils
+			.parsePersonIdent(TAGGER_LINE);
+
+	@Test
+	public void testTagSimple() throws Exception {
+		TagBuilder t = new TagBuilder();
+		t.setTag("sometag");
+		t.setObjectId(ObjectId.zeroId(), Constants.OBJ_COMMIT);
+		t.setEncoding(US_ASCII);
+		t.setMessage("Short message only");
+		t.setTagger(TAGGER);
+		String tag = new String(t.build(), UTF_8);
+		String expected = "object 0000000000000000000000000000000000000000\n"
+				+ "type commit\n" //
+				+ "tag sometag\n" //
+				+ "tagger " + TAGGER_LINE + '\n' //
+				+ "encoding US-ASCII\n" //
+				+ '\n' //
+				+ "Short message only";
+		assertEquals(expected, tag);
+	}
+
+	@Test
+	public void testTagWithSignatureShortMessageEndsInLF() throws Exception {
+		TagBuilder t = new TagBuilder();
+		t.setTag("sometag");
+		t.setObjectId(ObjectId.zeroId(), Constants.OBJ_COMMIT);
+		t.setEncoding(US_ASCII);
+		t.setMessage("Short message only\n");
+		t.setTagger(TAGGER);
+		t.setGpgSignature(new GpgSignature(SIGNATURE.getBytes(US_ASCII)));
+		String tag = new String(t.build(), UTF_8);
+		String expected = "object 0000000000000000000000000000000000000000\n"
+				+ "type commit\n" //
+				+ "tag sometag\n" //
+				+ "tagger " + TAGGER_LINE + '\n' //
+				+ "encoding US-ASCII\n" //
+				+ '\n' //
+				+ "Short message only\n" //
+				+ SIGNATURE + '\n';
+		assertEquals(expected, tag);
+	}
+
+	@Test
+	public void testTagWithSignatureMessageNoLF() {
+		TagBuilder t = new TagBuilder();
+		t.setTag("sometag");
+		t.setObjectId(ObjectId.zeroId(), Constants.OBJ_COMMIT);
+		t.setEncoding(US_ASCII);
+		t.setMessage("A message\n\nthat does not end in LF");
+		t.setTagger(TAGGER);
+		t.setGpgSignature(new GpgSignature(SIGNATURE.getBytes(US_ASCII)));
+		Throwable ex = assertThrows(Throwable.class, t::build);
+		assertEquals(JGitText.get().signedTagMessageNoLf, ex.getMessage());
+	}
+
+	@Test
+	public void testTagWithSignatureNoParagraphsMessage() throws Exception {
+		TagBuilder t = new TagBuilder();
+		t.setTag("sometag");
+		t.setObjectId(ObjectId.zeroId(), Constants.OBJ_COMMIT);
+		t.setEncoding(US_ASCII);
+		t.setMessage("A strange\ntag message\n");
+		t.setTagger(TAGGER);
+		t.setGpgSignature(new GpgSignature(SIGNATURE.getBytes(US_ASCII)));
+		String tag = new String(t.build(), UTF_8);
+		String expected = "object 0000000000000000000000000000000000000000\n"
+				+ "type commit\n" //
+				+ "tag sometag\n" //
+				+ "tagger " + TAGGER_LINE + '\n' //
+				+ "encoding US-ASCII\n" //
+				+ '\n' //
+				+ "A strange\ntag message\n" //
+				+ SIGNATURE + '\n';
+		assertEquals(expected, tag);
+	}
+
+	@Test
+	public void testTagWithSignatureLongMessage() throws Exception {
+		TagBuilder t = new TagBuilder();
+		t.setTag("sometag");
+		t.setObjectId(ObjectId.zeroId(), Constants.OBJ_COMMIT);
+		t.setMessage("Short message\n\nFollowed by explanations.\n");
+		t.setTagger(TAGGER);
+		t.setGpgSignature(new GpgSignature(SIGNATURE.getBytes(US_ASCII)));
+		String tag = new String(t.build(), UTF_8);
+		String expected = "object 0000000000000000000000000000000000000000\n"
+				+ "type commit\n" //
+				+ "tag sometag\n" //
+				+ "tagger " + TAGGER_LINE + '\n' //
+				+ '\n' //
+				+ "Short message\n\nFollowed by explanations.\n" //
+				+ SIGNATURE + '\n';
+		assertEquals(expected, tag);
+	}
+
+	@Test
+	public void testTagWithSignatureEmptyMessage() throws Exception {
+		TagBuilder t = new TagBuilder();
+		t.setTag("sometag");
+		t.setObjectId(ObjectId.zeroId(), Constants.OBJ_COMMIT);
+		t.setTagger(TAGGER);
+		t.setMessage("");
+		String emptyMsg = new String(t.build(), UTF_8);
+		t.setGpgSignature(new GpgSignature(SIGNATURE.getBytes(US_ASCII)));
+		String tag = new String(t.build(), UTF_8);
+		String expected = "object 0000000000000000000000000000000000000000\n"
+				+ "type commit\n" //
+				+ "tag sometag\n" //
+				+ "tagger " + TAGGER_LINE + '\n' //
+				+ '\n';
+		assertEquals(expected, emptyMsg);
+		assertEquals(expected + SIGNATURE + '\n', tag);
+	}
+
+	@Test
+	public void testTagWithSignatureOnly() throws Exception {
+		TagBuilder t = new TagBuilder();
+		t.setTag("sometag");
+		t.setObjectId(ObjectId.zeroId(), Constants.OBJ_COMMIT);
+		t.setTagger(TAGGER);
+		String emptyMsg = new String(t.build(), UTF_8);
+		t.setGpgSignature(new GpgSignature(SIGNATURE.getBytes(US_ASCII)));
+		String tag = new String(t.build(), UTF_8);
+		String expected = "object 0000000000000000000000000000000000000000\n"
+				+ "type commit\n" //
+				+ "tag sometag\n" //
+				+ "tagger " + TAGGER_LINE + '\n' //
+				+ '\n';
+		assertEquals(expected, emptyMsg);
+		assertEquals(expected + SIGNATURE + '\n', tag);
+	}
+
+}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/RevTagParseTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/RevTagParseTest.java
index b92a072..edddc33 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/RevTagParseTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/RevTagParseTest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008-2010, Google Inc. and others
+ * Copyright (C) 2008, 2020, Google Inc. 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
@@ -11,6 +11,7 @@
 package org.eclipse.jgit.revwalk;
 
 import static java.nio.charset.StandardCharsets.ISO_8859_1;
+import static java.nio.charset.StandardCharsets.US_ASCII;
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
@@ -18,6 +19,7 @@
 import static org.junit.Assert.assertSame;
 
 import java.io.ByteArrayOutputStream;
+import java.io.UnsupportedEncodingException;
 
 import org.eclipse.jgit.errors.CorruptObjectException;
 import org.eclipse.jgit.junit.RepositoryTestCase;
@@ -117,6 +119,7 @@
 		assertNotNull(c.getTagName());
 		assertEquals(name, c.getTagName());
 		assertEquals("", c.getFullMessage());
+		assertNull(c.getRawGpgSignature());
 
 		final PersonIdent cTagger = c.getTaggerIdent();
 		assertNotNull(cTagger);
@@ -128,13 +131,12 @@
 	public void testParseOldStyleNoTagger() throws Exception {
 		final ObjectId treeId = id("9788669ad918b6fcce64af8882fc9a81cb6aba67");
 		final String name = "v1.2.3.4.5";
-		final String message = "test\n" //
-				+ "\n" //
-				+ "-----BEGIN PGP SIGNATURE-----\n" //
+		final String fakeSignature = "-----BEGIN PGP SIGNATURE-----\n" //
 				+ "Version: GnuPG v1.4.1 (GNU/Linux)\n" //
 				+ "\n" //
 				+ "iD8DBQBC0b9oF3Y\n" //
-				+ "-----END PGP SIGNATURE------n";
+				+ "-----END PGP SIGNATURE-----";
+		final String message = "test\n\n" + fakeSignature + '\n';
 
 		final StringBuilder body = new StringBuilder();
 
@@ -167,6 +169,8 @@
 		assertEquals(name, c.getTagName());
 		assertEquals("test", c.getShortMessage());
 		assertEquals(message, c.getFullMessage());
+		assertEquals(fakeSignature + '\n',
+				new String(c.getRawGpgSignature(), US_ASCII));
 
 		assertNull(c.getTaggerIdent());
 	}
@@ -386,6 +390,108 @@
 	}
 
 	@Test
+	public void testParse_gpgSignature() throws Exception {
+		final String signature = "-----BEGIN PGP SIGNATURE-----\n\n"
+				+ "wsBcBAABCAAQBQJbGB4pCRBK7hj4Ov3rIwAAdHIIAENrvz23867ZgqrmyPemBEZP\n"
+				+ "U24B1Tlq/DWvce2buaxmbNQngKZ0pv2s8VMc11916WfTIC9EKvioatmpjduWvhqj\n"
+				+ "znQTFyiMor30pyYsfrqFuQZvqBW01o8GEWqLg8zjf9Rf0R3LlOEw86aT8CdHRlm6\n"
+				+ "wlb22xb8qoX4RB+LYfz7MhK5F+yLOPXZdJnAVbuyoMGRnDpwdzjL5Hj671+XJxN5\n"
+				+ "SasRdhxkkfw/ZnHxaKEc4juMz8Nziz27elRwhOQqlTYoXNJnsV//wy5Losd7aKi1\n"
+				+ "xXXyUpndEOmT0CIcKHrN/kbYoVL28OJaxoBuva3WYQaRrzEe3X02NMxZe9gkSqA=\n"
+				+ "=TClh\n" + "-----END PGP SIGNATURE-----";
+		ByteArrayOutputStream b = new ByteArrayOutputStream();
+		b.write("object 9788669ad918b6fcce64af8882fc9a81cb6aba67\n"
+				.getBytes(UTF_8));
+		b.write("type tree\n".getBytes(UTF_8));
+		b.write("tag v1.0\n".getBytes(UTF_8));
+		b.write("tagger t <t@example.com> 1218123387 +0700\n".getBytes(UTF_8));
+		b.write('\n');
+		b.write("message\n\n".getBytes(UTF_8));
+		b.write(signature.getBytes(US_ASCII));
+		b.write('\n');
+
+		RevTag t = new RevTag(id("9473095c4cb2f12aefe1db8a355fe3fafba42f67"));
+		try (RevWalk rw = new RevWalk(db)) {
+			t.parseCanonical(rw, b.toByteArray());
+		}
+
+		assertEquals("t", t.getTaggerIdent().getName());
+		assertEquals("message", t.getShortMessage());
+		assertEquals("message\n\n" + signature + '\n', t.getFullMessage());
+		String gpgSig = new String(t.getRawGpgSignature(), UTF_8);
+		assertEquals(signature + '\n', gpgSig);
+	}
+
+	@Test
+	public void testParse_gpgSignature2() throws Exception {
+		final String signature = "-----BEGIN PGP SIGNATURE-----\n\n"
+				+ "wsBcBAABCAAQBQJbGB4pCRBK7hj4Ov3rIwAAdHIIAENrvz23867ZgqrmyPemBEZP\n"
+				+ "U24B1Tlq/DWvce2buaxmbNQngKZ0pv2s8VMc11916WfTIC9EKvioatmpjduWvhqj\n"
+				+ "znQTFyiMor30pyYsfrqFuQZvqBW01o8GEWqLg8zjf9Rf0R3LlOEw86aT8CdHRlm6\n"
+				+ "wlb22xb8qoX4RB+LYfz7MhK5F+yLOPXZdJnAVbuyoMGRnDpwdzjL5Hj671+XJxN5\n"
+				+ "SasRdhxkkfw/ZnHxaKEc4juMz8Nziz27elRwhOQqlTYoXNJnsV//wy5Losd7aKi1\n"
+				+ "xXXyUpndEOmT0CIcKHrN/kbYoVL28OJaxoBuva3WYQaRrzEe3X02NMxZe9gkSqA=\n"
+				+ "=TClh\n" + "-----END PGP SIGNATURE-----";
+		ByteArrayOutputStream b = new ByteArrayOutputStream();
+		b.write("object 9788669ad918b6fcce64af8882fc9a81cb6aba67\n"
+				.getBytes(UTF_8));
+		b.write("type tree\n".getBytes(UTF_8));
+		b.write("tag v1.0\n".getBytes(UTF_8));
+		b.write("tagger t <t@example.com> 1218123387 +0700\n".getBytes(UTF_8));
+		b.write('\n');
+		String message = "message\n\n" + signature.replace("xXXy", "aAAb")
+				+ '\n';
+		b.write(message.getBytes(UTF_8));
+		b.write(signature.getBytes(US_ASCII));
+		b.write('\n');
+
+		RevTag t = new RevTag(id("9473095c4cb2f12aefe1db8a355fe3fafba42f67"));
+		try (RevWalk rw = new RevWalk(db)) {
+			t.parseCanonical(rw, b.toByteArray());
+		}
+
+		assertEquals("t", t.getTaggerIdent().getName());
+		assertEquals("message", t.getShortMessage());
+		assertEquals(message + signature + '\n', t.getFullMessage());
+		String gpgSig = new String(t.getRawGpgSignature(), UTF_8);
+		assertEquals(signature + '\n', gpgSig);
+	}
+
+	@Test
+	public void testParse_gpgSignature3() throws Exception {
+		final String signature = "-----BEGIN PGP SIGNATURE-----\n\n"
+				+ "wsBcBAABCAAQBQJbGB4pCRBK7hj4Ov3rIwAAdHIIAENrvz23867ZgqrmyPemBEZP\n"
+				+ "U24B1Tlq/DWvce2buaxmbNQngKZ0pv2s8VMc11916WfTIC9EKvioatmpjduWvhqj\n"
+				+ "znQTFyiMor30pyYsfrqFuQZvqBW01o8GEWqLg8zjf9Rf0R3LlOEw86aT8CdHRlm6\n"
+				+ "wlb22xb8qoX4RB+LYfz7MhK5F+yLOPXZdJnAVbuyoMGRnDpwdzjL5Hj671+XJxN5\n"
+				+ "SasRdhxkkfw/ZnHxaKEc4juMz8Nziz27elRwhOQqlTYoXNJnsV//wy5Losd7aKi1\n"
+				+ "xXXyUpndEOmT0CIcKHrN/kbYoVL28OJaxoBuva3WYQaRrzEe3X02NMxZe9gkSqA=\n"
+				+ "=TClh\n" + "-----END PGP SIGNATURE-----";
+		ByteArrayOutputStream b = new ByteArrayOutputStream();
+		b.write("object 9788669ad918b6fcce64af8882fc9a81cb6aba67\n"
+				.getBytes(UTF_8));
+		b.write("type tree\n".getBytes(UTF_8));
+		b.write("tag v1.0\n".getBytes(UTF_8));
+		b.write("tagger t <t@example.com> 1218123387 +0700\n".getBytes(UTF_8));
+		b.write('\n');
+		String message = "message\n\n-----BEGIN PGP SIGNATURE-----\n";
+		b.write(message.getBytes(UTF_8));
+		b.write(signature.getBytes(US_ASCII));
+		b.write('\n');
+
+		RevTag t = new RevTag(id("9473095c4cb2f12aefe1db8a355fe3fafba42f67"));
+		try (RevWalk rw = new RevWalk(db)) {
+			t.parseCanonical(rw, b.toByteArray());
+		}
+
+		assertEquals("t", t.getTaggerIdent().getName());
+		assertEquals("message", t.getShortMessage());
+		assertEquals(message + signature + '\n', t.getFullMessage());
+		String gpgSig = new String(t.getRawGpgSignature(), UTF_8);
+		assertEquals(signature + '\n', gpgSig);
+	}
+
+	@Test
 	public void testParse_NoMessage() throws Exception {
 		final String msg = "";
 		final RevTag c = create(msg);
@@ -447,7 +553,8 @@
 	}
 
 	@Test
-	public void testParse_PublicParseMethod() throws CorruptObjectException {
+	public void testParse_PublicParseMethod()
+			throws CorruptObjectException, UnsupportedEncodingException {
 		TagBuilder src = new TagBuilder();
 		try (ObjectInserter.Formatter fmt = new ObjectInserter.Formatter()) {
 			src.setObjectId(fmt.idFor(Constants.OBJ_TREE, new byte[] {}),
diff --git a/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties b/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
index 12902b9..6d15464 100644
--- a/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
+++ b/org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
@@ -617,6 +617,7 @@
 shortReadOfBlock=Short read of block.
 shortReadOfOptionalDIRCExtensionExpectedAnotherBytes=Short read of optional DIRC extension {0}; expected another {1} bytes within the section.
 shortSkipOfBlock=Short skip of block.
+signedTagMessageNoLf=A non-empty message of a signed tag must end in LF.
 signingNotSupportedOnTag=Signing isn't supported on tag operations yet.
 signingServiceUnavailable=Signing service is not available
 similarityScoreMustBeWithinBounds=Similarity score must be between 0 and 100.
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
index 892657d..a7daed1 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
@@ -645,6 +645,7 @@
 	/***/ public String shortReadOfBlock;
 	/***/ public String shortReadOfOptionalDIRCExtensionExpectedAnotherBytes;
 	/***/ public String shortSkipOfBlock;
+	/***/ public String signedTagMessageNoLf;
 	/***/ public String signingNotSupportedOnTag;
 	/***/ public String signingServiceUnavailable;
 	/***/ public String similarityScoreMustBeWithinBounds;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/CommitBuilder.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/CommitBuilder.java
index 4f93fda..1665f05 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/CommitBuilder.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/CommitBuilder.java
@@ -1,7 +1,7 @@
 /*
  * Copyright (C) 2007, Dave Watson <dwatson@mimvista.com>
- * Copyright (C) 2006-2007, Robin Rosenberg <robin.rosenberg@dewire.com>
- * Copyright (C) 2006-2007, Shawn O. Pearce <spearce@spearce.org> and others
+ * Copyright (C) 2006, 2007, Robin Rosenberg <robin.rosenberg@dewire.com>
+ * Copyright (C) 2006, 2020, Shawn O. Pearce <spearce@spearce.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
@@ -16,14 +16,11 @@
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
-import java.io.OutputStream;
 import java.io.OutputStreamWriter;
 import java.io.UnsupportedEncodingException;
 import java.nio.charset.Charset;
-import java.text.MessageFormat;
 import java.util.List;
 
-import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.util.References;
 
 /**
@@ -37,7 +34,7 @@
  * and obtain a {@link org.eclipse.jgit.revwalk.RevCommit} instance by calling
  * {@link org.eclipse.jgit.revwalk.RevWalk#parseCommit(AnyObjectId)}.
  */
-public class CommitBuilder {
+public class CommitBuilder extends ObjectBuilder {
 	private static final ObjectId[] EMPTY_OBJECTID_LIST = new ObjectId[0];
 
 	private static final byte[] htree = Constants.encodeASCII("tree"); //$NON-NLS-1$
@@ -50,28 +47,17 @@
 
 	private static final byte[] hgpgsig = Constants.encodeASCII("gpgsig"); //$NON-NLS-1$
 
-	private static final byte[] hencoding = Constants.encodeASCII("encoding"); //$NON-NLS-1$
-
 	private ObjectId treeId;
 
 	private ObjectId[] parentIds;
 
-	private PersonIdent author;
-
 	private PersonIdent committer;
 
-	private GpgSignature gpgSignature;
-
-	private String message;
-
-	private Charset encoding;
-
 	/**
 	 * Initialize an empty commit.
 	 */
 	public CommitBuilder() {
 		parentIds = EMPTY_OBJECTID_LIST;
-		encoding = UTF_8;
 	}
 
 	/**
@@ -98,8 +84,9 @@
 	 *
 	 * @return the author of this commit (who wrote it).
 	 */
+	@Override
 	public PersonIdent getAuthor() {
-		return author;
+		return super.getAuthor();
 	}
 
 	/**
@@ -108,8 +95,9 @@
 	 * @param newAuthor
 	 *            the new author. Should not be null.
 	 */
+	@Override
 	public void setAuthor(PersonIdent newAuthor) {
-		author = newAuthor;
+		super.setAuthor(newAuthor);
 	}
 
 	/**
@@ -132,38 +120,6 @@
 	}
 
 	/**
-	 * Set the GPG signature of this commit.
-	 * <p>
-	 * Note, the signature set here will change the payload of the commit, i.e.
-	 * the output of {@link #build()} will include the signature. Thus, the
-	 * typical flow will be:
-	 * <ol>
-	 * <li>call {@link #build()} without a signature set to obtain payload</li>
-	 * <li>create {@link GpgSignature} from payload</li>
-	 * <li>set {@link GpgSignature}</li>
-	 * </ol>
-	 * </p>
-	 *
-	 * @param newSignature
-	 *            the signature to set or <code>null</code> to unset
-	 * @since 5.3
-	 */
-	public void setGpgSignature(GpgSignature newSignature) {
-		gpgSignature = newSignature;
-	}
-
-	/**
-	 * Get the GPG signature of this commit.
-	 *
-	 * @return the GPG signature of this commit, maybe <code>null</code> if the
-	 *         commit is not to be signed
-	 * @since 5.3
-	 */
-	public GpgSignature getGpgSignature() {
-		return gpgSignature;
-	}
-
-	/**
 	 * Get the ancestors of this commit.
 	 *
 	 * @return the ancestors of this commit. Never null.
@@ -239,25 +195,6 @@
 	}
 
 	/**
-	 * Get the complete commit message.
-	 *
-	 * @return the complete commit message.
-	 */
-	public String getMessage() {
-		return message;
-	}
-
-	/**
-	 * Set the commit message.
-	 *
-	 * @param newMessage
-	 *            the commit message. Should not be null.
-	 */
-	public void setMessage(String newMessage) {
-		message = newMessage;
-	}
-
-	/**
 	 * Set the encoding for the commit information.
 	 *
 	 * @param encodingName
@@ -267,37 +204,10 @@
 	 */
 	@Deprecated
 	public void setEncoding(String encodingName) {
-		encoding = Charset.forName(encodingName);
+		setEncoding(Charset.forName(encodingName));
 	}
 
-	/**
-	 * Set the encoding for the commit information.
-	 *
-	 * @param enc
-	 *            the encoding to use.
-	 */
-	public void setEncoding(Charset enc) {
-		encoding = enc;
-	}
-
-	/**
-	 * Get the encoding that should be used for the commit message text.
-	 *
-	 * @return the encoding that should be used for the commit message text.
-	 */
-	public Charset getEncoding() {
-		return encoding;
-	}
-
-	/**
-	 * Format this builder's state as a commit object.
-	 *
-	 * @return this object in the canonical commit format, suitable for storage
-	 *         in a repository.
-	 * @throws java.io.UnsupportedEncodingException
-	 *             the encoding specified by {@link #getEncoding()} is not
-	 *             supported by this Java runtime.
-	 */
+	@Override
 	public byte[] build() throws UnsupportedEncodingException {
 		ByteArrayOutputStream os = new ByteArrayOutputStream();
 		OutputStreamWriter w = new OutputStreamWriter(os, getEncoding());
@@ -326,19 +236,16 @@
 			w.flush();
 			os.write('\n');
 
-			if (getGpgSignature() != null) {
+			GpgSignature signature = getGpgSignature();
+			if (signature != null) {
 				os.write(hgpgsig);
 				os.write(' ');
-				writeGpgSignatureString(getGpgSignature().toExternalString(), os);
+				writeMultiLineHeader(signature.toExternalString(), os,
+						true);
 				os.write('\n');
 			}
 
-			if (!References.isSameObject(getEncoding(), UTF_8)) {
-				os.write(hencoding);
-				os.write(' ');
-				os.write(Constants.encodeASCII(getEncoding().name()));
-				os.write('\n');
-			}
+			writeEncoding(getEncoding(), os);
 
 			os.write('\n');
 
@@ -356,58 +263,6 @@
 	}
 
 	/**
-	 * Writes signature to output as per <a href=
-	 * "https://github.com/git/git/blob/master/Documentation/technical/signature-format.txt#L66,L89">gpgsig
-	 * header</a>.
-	 * <p>
-	 * CRLF and CR will be sanitized to LF and signature will have a hanging
-	 * indent of one space starting with line two. A trailing line break is
-	 * <em>not</em> written; the caller is supposed to terminate the GPG
-	 * signature header by writing a single newline.
-	 * </p>
-	 *
-	 * @param in
-	 *            signature string with line breaks
-	 * @param out
-	 *            output stream
-	 * @throws IOException
-	 *             thrown by the output stream
-	 * @throws IllegalArgumentException
-	 *             if the signature string contains non 7-bit ASCII chars
-	 */
-	static void writeGpgSignatureString(String in, OutputStream out)
-			throws IOException, IllegalArgumentException {
-		int length = in.length();
-		for (int i = 0; i < length; ++i) {
-			char ch = in.charAt(i);
-			switch (ch) {
-			case '\r':
-				if (i + 1 < length && in.charAt(i + 1) == '\n') {
-					++i;
-				}
-				if (i + 1 < length) {
-					out.write('\n');
-					out.write(' ');
-				}
-				break;
-			case '\n':
-				if (i + 1 < length) {
-					out.write('\n');
-					out.write(' ');
-				}
-				break;
-			default:
-				// sanity check
-				if (ch > 127)
-					throw new IllegalArgumentException(MessageFormat
-							.format(JGitText.get().notASCIIString, in));
-				out.write(ch);
-				break;
-			}
-		}
-	}
-
-	/**
 	 * Format this builder's state as a commit object.
 	 *
 	 * @return this object in the canonical commit format, suitable for storage
@@ -439,7 +294,7 @@
 		}
 
 		r.append("author ");
-		r.append(author != null ? author.toString() : "NOT_SET");
+		r.append(getAuthor() != null ? getAuthor().toString() : "NOT_SET");
 		r.append("\n");
 
 		r.append("committer ");
@@ -447,17 +302,20 @@
 		r.append("\n");
 
 		r.append("gpgSignature ");
-		r.append(gpgSignature != null ? gpgSignature.toString() : "NOT_SET");
+		GpgSignature signature = getGpgSignature();
+		r.append(signature != null ? signature.toString()
+				: "NOT_SET");
 		r.append("\n");
 
-		if (encoding != null && !References.isSameObject(encoding, UTF_8)) {
+		Charset encoding = getEncoding();
+		if (!References.isSameObject(encoding, UTF_8)) {
 			r.append("encoding ");
 			r.append(encoding.name());
 			r.append("\n");
 		}
 
 		r.append("\n");
-		r.append(message != null ? message : "");
+		r.append(getMessage() != null ? getMessage() : "");
 		r.append("}");
 		return r.toString();
 	}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/GpgObjectSigner.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/GpgObjectSigner.java
new file mode 100644
index 0000000..6fb7677
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/GpgObjectSigner.java
@@ -0,0 +1,59 @@
+/*
+ * 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.lib;
+
+import org.eclipse.jgit.annotations.NonNull;
+import org.eclipse.jgit.annotations.Nullable;
+import org.eclipse.jgit.api.errors.CanceledException;
+import org.eclipse.jgit.transport.CredentialsProvider;
+
+/**
+ * Creates GPG signatures for Git objects.
+ *
+ * @since 5.11
+ */
+public interface GpgObjectSigner {
+
+	/**
+	 * Signs the specified object.
+	 *
+	 * <p>
+	 * Implementors should obtain the payload for signing from the specified
+	 * object via {@link ObjectBuilder#build()} and create a proper
+	 * {@link GpgSignature}. The generated signature must be set on the
+	 * specified {@code object} (see
+	 * {@link ObjectBuilder#setGpgSignature(GpgSignature)}).
+	 * </p>
+	 * <p>
+	 * Any existing signature on the object must be discarded prior obtaining
+	 * the payload via {@link ObjectBuilder#build()}.
+	 * </p>
+	 *
+	 * @param object
+	 *            the object to sign (must not be {@code null} and must be
+	 *            complete to allow proper calculation of payload)
+	 * @param gpgSigningKey
+	 *            the signing key to locate (passed as is to the GPG signing
+	 *            tool as is; eg., value of <code>user.signingkey</code>)
+	 * @param committer
+	 *            the signing identity (to help with key lookup in case signing
+	 *            key is not specified)
+	 * @param credentialsProvider
+	 *            provider to use when querying for signing key credentials (eg.
+	 *            passphrase)
+	 * @throws CanceledException
+	 *             when signing was canceled (eg., user aborted when entering
+	 *             passphrase)
+	 */
+	void signObject(@NonNull ObjectBuilder object,
+			@Nullable String gpgSigningKey, @NonNull PersonIdent committer,
+			CredentialsProvider credentialsProvider) throws CanceledException;
+
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectBuilder.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectBuilder.java
new file mode 100644
index 0000000..4b7054f
--- /dev/null
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectBuilder.java
@@ -0,0 +1,225 @@
+/*
+ * 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.lib;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.io.UnsupportedEncodingException;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import java.text.MessageFormat;
+import java.util.Objects;
+
+import org.eclipse.jgit.annotations.NonNull;
+import org.eclipse.jgit.annotations.Nullable;
+import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.util.References;
+
+/**
+ * Common base class for {@link CommitBuilder} and {@link TagBuilder}.
+ *
+ * @since 5.11
+ */
+public abstract class ObjectBuilder {
+
+	/** Byte representation of "encoding". */
+	private static final byte[] hencoding = Constants.encodeASCII("encoding"); //$NON-NLS-1$
+
+	private PersonIdent author;
+
+	private GpgSignature gpgSignature;
+
+	private String message;
+
+	private Charset encoding = StandardCharsets.UTF_8;
+
+	/**
+	 * Retrieves the author of this object.
+	 *
+	 * @return the author of this object, or {@code null} if not set yet
+	 */
+	protected PersonIdent getAuthor() {
+		return author;
+	}
+
+	/**
+	 * Sets the author (name, email address, and date) of this object.
+	 *
+	 * @param newAuthor
+	 *            the new author, must be non-{@code null}
+	 */
+	protected void setAuthor(PersonIdent newAuthor) {
+		author = Objects.requireNonNull(newAuthor);
+	}
+
+	/**
+	 * Sets the GPG signature of this object.
+	 * <p>
+	 * Note, the signature set here will change the payload of the object, i.e.
+	 * the output of {@link #build()} will include the signature. Thus, the
+	 * typical flow will be:
+	 * <ol>
+	 * <li>call {@link #build()} without a signature set to obtain payload</li>
+	 * <li>create {@link GpgSignature} from payload</li>
+	 * <li>set {@link GpgSignature}</li>
+	 * </ol>
+	 * </p>
+	 *
+	 * @param gpgSignature
+	 *            the signature to set or {@code null} to unset
+	 * @since 5.3
+	 */
+	public void setGpgSignature(@Nullable GpgSignature gpgSignature) {
+		this.gpgSignature = gpgSignature;
+	}
+
+	/**
+	 * Retrieves the GPG signature of this object.
+	 *
+	 * @return the GPG signature of this object, or {@code null} if the object
+	 *         is not signed
+	 * @since 5.3
+	 */
+	@Nullable
+	public GpgSignature getGpgSignature() {
+		return gpgSignature;
+	}
+
+	/**
+	 * Retrieves the complete message of the object.
+	 *
+	 * @return the complete message; can be {@code null}.
+	 */
+	@Nullable
+	public String getMessage() {
+		return message;
+	}
+
+	/**
+	 * Sets the message (commit message, or message of an annotated tag).
+	 *
+	 * @param message
+	 *            the message.
+	 */
+	public void setMessage(@Nullable String message) {
+		this.message = message;
+	}
+
+	/**
+	 * Retrieves the encoding that should be used for the message text.
+	 *
+	 * @return the encoding that should be used for the message text.
+	 */
+	@NonNull
+	public Charset getEncoding() {
+		return encoding;
+	}
+
+	/**
+	 * Sets the encoding for the object message.
+	 *
+	 * @param encoding
+	 *            the encoding to use.
+	 */
+	public void setEncoding(@NonNull Charset encoding) {
+		this.encoding = encoding;
+	}
+
+	/**
+	 * Format this builder's state as a git object.
+	 *
+	 * @return this object in the canonical git format, suitable for storage in
+	 *         a repository.
+	 * @throws java.io.UnsupportedEncodingException
+	 *             the encoding specified by {@link #getEncoding()} is not
+	 *             supported by this Java runtime.
+	 */
+	@NonNull
+	public abstract byte[] build() throws UnsupportedEncodingException;
+
+	/**
+	 * Writes signature to output as per <a href=
+	 * "https://github.com/git/git/blob/master/Documentation/technical/signature-format.txt#L66,L89">gpgsig
+	 * header</a>.
+	 * <p>
+	 * CRLF and CR will be sanitized to LF and signature will have a hanging
+	 * indent of one space starting with line two. A trailing line break is
+	 * <em>not</em> written; the caller is supposed to terminate the GPG
+	 * signature header by writing a single newline.
+	 * </p>
+	 *
+	 * @param in
+	 *            signature string with line breaks
+	 * @param out
+	 *            output stream
+	 * @param enforceAscii
+	 *            whether to throw {@link IllegalArgumentException} if non-ASCII
+	 *            characters are encountered
+	 * @throws IOException
+	 *             thrown by the output stream
+	 * @throws IllegalArgumentException
+	 *             if the signature string contains non 7-bit ASCII chars and
+	 *             {@code enforceAscii == true}
+	 */
+	static void writeMultiLineHeader(@NonNull String in,
+			@NonNull OutputStream out, boolean enforceAscii)
+			throws IOException, IllegalArgumentException {
+		int length = in.length();
+		for (int i = 0; i < length; ++i) {
+			char ch = in.charAt(i);
+			switch (ch) {
+			case '\r':
+				if (i + 1 < length && in.charAt(i + 1) == '\n') {
+					++i;
+				}
+				if (i + 1 < length) {
+					out.write('\n');
+					out.write(' ');
+				}
+				break;
+			case '\n':
+				if (i + 1 < length) {
+					out.write('\n');
+					out.write(' ');
+				}
+				break;
+			default:
+				// sanity check
+				if (ch > 127 && enforceAscii)
+					throw new IllegalArgumentException(MessageFormat
+							.format(JGitText.get().notASCIIString, in));
+				out.write(ch);
+				break;
+			}
+		}
+	}
+
+	/**
+	 * Writes an "encoding" header.
+	 *
+	 * @param encoding
+	 *            to write
+	 * @param out
+	 *            to write to
+	 * @throws IOException
+	 *             if writing fails
+	 */
+	static void writeEncoding(@NonNull Charset encoding,
+			@NonNull OutputStream out) throws IOException {
+		if (!References.isSameObject(encoding, UTF_8)) {
+			out.write(hencoding);
+			out.write(' ');
+			out.write(Constants.encodeASCII(encoding.name()));
+			out.write('\n');
+		}
+	}
+}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/TagBuilder.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/TagBuilder.java
index 71f0115..facb4a5 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/TagBuilder.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/TagBuilder.java
@@ -1,7 +1,7 @@
 /*
- * Copyright (C) 2006-2008, Robin Rosenberg <robin.rosenberg@dewire.com>
+ * Copyright (C) 2006, 2008, Robin Rosenberg <robin.rosenberg@dewire.com>
  * Copyright (C) 2008, Shawn O. Pearce <spearce@spearce.org>
- * Copyright (C) 2010, Chris Aniszczyk <caniszczyk@gmail.com> and others
+ * Copyright (C) 2010, 2020, Chris Aniszczyk <caniszczyk@gmail.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
@@ -17,8 +17,13 @@
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.OutputStreamWriter;
+import java.io.UnsupportedEncodingException;
+import java.nio.charset.Charset;
 
+import org.eclipse.jgit.api.errors.JGitInternalException;
+import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.revwalk.RevObject;
+import org.eclipse.jgit.util.References;
 
 /**
  * Mutable builder to construct an annotated tag recording a project state.
@@ -30,17 +35,22 @@
  * and obtain a {@link org.eclipse.jgit.revwalk.RevTag} instance by calling
  * {@link org.eclipse.jgit.revwalk.RevWalk#parseTag(AnyObjectId)}.
  */
-public class TagBuilder {
+public class TagBuilder extends ObjectBuilder {
+
+	private static final byte[] hobject = Constants.encodeASCII("object"); //$NON-NLS-1$
+
+	private static final byte[] htype = Constants.encodeASCII("type"); //$NON-NLS-1$
+
+	private static final byte[] htag = Constants.encodeASCII("tag"); //$NON-NLS-1$
+
+	private static final byte[] htagger = Constants.encodeASCII("tagger"); //$NON-NLS-1$
+
 	private ObjectId object;
 
 	private int type = Constants.OBJ_BAD;
 
 	private String tag;
 
-	private PersonIdent tagger;
-
-	private String message;
-
 	/**
 	 * Get the type of object this tag refers to.
 	 *
@@ -109,7 +119,7 @@
 	 * @return creator of this tag. May be null.
 	 */
 	public PersonIdent getTagger() {
-		return tagger;
+		return getAuthor();
 	}
 
 	/**
@@ -119,26 +129,7 @@
 	 *            the creator. May be null.
 	 */
 	public void setTagger(PersonIdent taggerIdent) {
-		tagger = taggerIdent;
-	}
-
-	/**
-	 * Get the complete commit message.
-	 *
-	 * @return the complete commit message.
-	 */
-	public String getMessage() {
-		return message;
-	}
-
-	/**
-	 * Set the tag's message.
-	 *
-	 * @param newMessage
-	 *            the tag's message.
-	 */
-	public void setMessage(String newMessage) {
-		message = newMessage;
+		setAuthor(taggerIdent);
 	}
 
 	/**
@@ -147,31 +138,65 @@
 	 * @return this object in the canonical annotated tag format, suitable for
 	 *         storage in a repository.
 	 */
-	public byte[] build() {
+	@Override
+	public byte[] build() throws UnsupportedEncodingException {
 		ByteArrayOutputStream os = new ByteArrayOutputStream();
 		try (OutputStreamWriter w = new OutputStreamWriter(os,
-				UTF_8)) {
-			w.write("object "); //$NON-NLS-1$
-			getObjectId().copyTo(w);
-			w.write('\n');
+				getEncoding())) {
 
-			w.write("type "); //$NON-NLS-1$
-			w.write(Constants.typeString(getObjectType()));
-			w.write("\n"); //$NON-NLS-1$
+			os.write(hobject);
+			os.write(' ');
+			getObjectId().copyTo(os);
+			os.write('\n');
 
-			w.write("tag "); //$NON-NLS-1$
+			os.write(htype);
+			os.write(' ');
+			os.write(Constants
+					.encodeASCII(Constants.typeString(getObjectType())));
+			os.write('\n');
+
+			os.write(htag);
+			os.write(' ');
 			w.write(getTag());
-			w.write("\n"); //$NON-NLS-1$
+			w.flush();
+			os.write('\n');
 
 			if (getTagger() != null) {
-				w.write("tagger "); //$NON-NLS-1$
+				os.write(htagger);
+				os.write(' ');
 				w.write(getTagger().toExternalString());
-				w.write('\n');
+				w.flush();
+				os.write('\n');
 			}
 
-			w.write('\n');
-			if (getMessage() != null)
-				w.write(getMessage());
+			writeEncoding(getEncoding(), os);
+
+			os.write('\n');
+			String msg = getMessage();
+			if (msg != null) {
+				w.write(msg);
+				w.flush();
+			}
+
+			GpgSignature signature = getGpgSignature();
+			if (signature != null) {
+				if (msg != null && !msg.isEmpty() && !msg.endsWith("\n")) { //$NON-NLS-1$
+					// If signed, the message *must* end with a linefeed
+					// character, otherwise signature verification will fail.
+					// (The signature will have been computed over the payload
+					// containing the message without LF, but will be verified
+					// against a payload with the LF.) The signature must start
+					// on a new line.
+					throw new JGitInternalException(
+							JGitText.get().signedTagMessageNoLf);
+				}
+				String externalForm = signature.toExternalString();
+				w.write(externalForm);
+				w.flush();
+				if (!externalForm.endsWith("\n")) { //$NON-NLS-1$
+					os.write('\n');
+				}
+			}
 		} catch (IOException err) {
 			// This should never occur, the only way to get it above is
 			// for the ByteArrayOutputStream to throw, but it doesn't.
@@ -185,10 +210,17 @@
 	 * Format this builder's state as an annotated tag object.
 	 *
 	 * @return this object in the canonical annotated tag format, suitable for
-	 *         storage in a repository.
+	 *         storage in a repository, or {@code null} if the tag cannot be
+	 *         encoded
+	 * @deprecated since 5.11; use {@link #build()} instead
 	 */
+	@Deprecated
 	public byte[] toByteArray() {
-		return build();
+		try {
+			return build();
+		} catch (UnsupportedEncodingException e) {
+			return null;
+		}
 	}
 
 	/** {@inheritDoc} */
@@ -211,14 +243,23 @@
 		r.append(tag != null ? tag : "NOT_SET");
 		r.append("\n");
 
-		if (tagger != null) {
+		if (getTagger() != null) {
 			r.append("tagger ");
-			r.append(tagger);
+			r.append(getTagger());
+			r.append("\n");
+		}
+
+		Charset encoding = getEncoding();
+		if (!References.isSameObject(encoding, UTF_8)) {
+			r.append("encoding ");
+			r.append(encoding.name());
 			r.append("\n");
 		}
 
 		r.append("\n");
-		r.append(message != null ? message : "");
+		r.append(getMessage() != null ? getMessage() : "");
+		GpgSignature signature = getGpgSignature();
+		r.append(signature != null ? signature.toExternalString() : "");
 		r.append("}");
 		return r.toString();
 	}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevTag.java b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevTag.java
index cac2571..3bcdfaf 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevTag.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/revwalk/RevTag.java
@@ -18,7 +18,9 @@
 import java.nio.charset.Charset;
 import java.nio.charset.IllegalCharsetNameException;
 import java.nio.charset.UnsupportedCharsetException;
+import java.util.Arrays;
 
+import org.eclipse.jgit.annotations.Nullable;
 import org.eclipse.jgit.errors.CorruptObjectException;
 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
 import org.eclipse.jgit.errors.MissingObjectException;
@@ -35,6 +37,10 @@
  * An annotated tag.
  */
 public class RevTag extends RevObject {
+
+	private static final byte[] hSignature = Constants
+			.encodeASCII("-----BEGIN PGP SIGNATURE-----"); //$NON-NLS-1$
+
 	/**
 	 * Parse an annotated tag from its canonical format.
 	 *
@@ -171,6 +177,62 @@
 		return RawParseUtils.parsePersonIdent(raw, nameB);
 	}
 
+	private static int nextStart(byte[] prefix, byte[] buffer, int from) {
+		int stop = buffer.length - prefix.length + 1;
+		int ptr = from;
+		if (ptr > 0) {
+			ptr = RawParseUtils.nextLF(buffer, ptr - 1);
+		}
+		while (ptr < stop) {
+			int lineStart = ptr;
+			boolean found = true;
+			for (byte element : prefix) {
+				if (element != buffer[ptr++]) {
+					found = false;
+					break;
+				}
+			}
+			if (found) {
+				return lineStart;
+			}
+			do {
+				ptr = RawParseUtils.nextLF(buffer, ptr);
+			} while (ptr < stop && buffer[ptr] == '\n');
+		}
+		return -1;
+	}
+
+	/**
+	 * Parse the GPG signature from the raw buffer.
+	 *
+	 * @return contents of the GPG signature; {@code null} if the tag was not
+	 *         signed.
+	 * @since 5.11
+	 */
+	@Nullable
+	public final byte[] getRawGpgSignature() {
+		byte[] raw = buffer;
+		int msgB = RawParseUtils.tagMessage(raw, 0);
+		if (msgB < 0) {
+			return null;
+		}
+		// Find the last signature start and return the rest
+		int start = nextStart(hSignature, raw, msgB);
+		if (start < 0) {
+			return null;
+		}
+		int next = RawParseUtils.nextLF(raw, start);
+		while (next < raw.length) {
+			int newStart = nextStart(hSignature, raw, next);
+			if (newStart < 0) {
+				break;
+			}
+			start = newStart;
+			next = RawParseUtils.nextLF(raw, start);
+		}
+		return Arrays.copyOfRange(raw, start, raw.length);
+	}
+
 	/**
 	 * Parse the complete tag message and decode it to a string.
 	 * <p>