diff --git a/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/TestRepository.java b/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/TestRepository.java
index 6e1f1db39..7a95ccd36 100644
--- a/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/TestRepository.java
+++ b/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/TestRepository.java
@@ -368,7 +368,7 @@ public RevCommit commit(final int secDelta, final RevTree tree,
 		c.setMessage("");
 		ObjectId id;
 		try {
-			id = inserter.insert(Constants.OBJ_COMMIT, inserter.format(c));
+			id = inserter.insert(c);
 			inserter.flush();
 		} finally {
 			inserter.release();
@@ -405,7 +405,7 @@ public RevTag tag(final String name, final RevObject dst) throws Exception {
 		t.setMessage("");
 		ObjectId id;
 		try {
-			id = inserter.insert(Constants.OBJ_TAG, inserter.format(t));
+			id = inserter.insert(t);
 			inserter.flush();
 		} finally {
 			inserter.release();
@@ -822,8 +822,7 @@ public RevCommit create() throws Exception {
 				ObjectId commitId;
 				try {
 					c.setTreeId(tree.writeTree(inserter));
-					commitId = inserter.insert(Constants.OBJ_COMMIT, inserter
-							.format(c));
+					commitId = inserter.insert(c);
 					inserter.flush();
 				} finally {
 					inserter.release();
diff --git a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Tag.java b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Tag.java
index 0ab19b6bb..19454b186 100644
--- a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Tag.java
+++ b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Tag.java
@@ -100,7 +100,7 @@ protected void run() throws Exception {
 			tag.setTagger(new PersonIdent(db));
 			tag.setMessage(message.replaceAll("\r", ""));
 			tag.setTag(shortName);
-			id = inserter.insert(Constants.OBJ_TAG, inserter.format(tag));
+			id = inserter.insert(tag);
 			inserter.flush();
 		} finally {
 			inserter.release();
diff --git a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/RebuildCommitGraph.java b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/RebuildCommitGraph.java
index ab4412871..b01734e00 100644
--- a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/RebuildCommitGraph.java
+++ b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/debug/RebuildCommitGraph.java
@@ -197,7 +197,7 @@ private void recreateCommitGraph() throws IOException {
 				newc.setCommitter(newc.getAuthor());
 				newc.setParentIds(newParents);
 				newc.setMessage("ORIGINAL " + t.oldId.name() + "\n");
-				t.newId = oi.insert(Constants.OBJ_COMMIT,oi.format(newc));
+				t.newId = oi.insert(newc);
 				rewrites.put(t.oldId, t.newId);
 				pm.update(1);
 			}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/CherryPickTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/CherryPickTest.java
index 876b98636..12fdec2b6 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/CherryPickTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/CherryPickTest.java
@@ -45,7 +45,6 @@
 package org.eclipse.jgit.merge;
 
 import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
-import static org.eclipse.jgit.lib.Constants.OBJ_COMMIT;
 
 import org.eclipse.jgit.dircache.DirCache;
 import org.eclipse.jgit.dircache.DirCacheBuilder;
@@ -137,7 +136,7 @@ private ObjectId commit(final ObjectInserter odi, final DirCache treeB,
 		c.setCommitter(c.getAuthor());
 		c.setParentIds(parentIds);
 		c.setMessage("Tree " + c.getTreeId().name());
-		ObjectId id = odi.insert(OBJ_COMMIT, odi.format(c));
+		ObjectId id = odi.insert(c);
 		odi.flush();
 		return id;
 	}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/SimpleMergeTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/SimpleMergeTest.java
index 5e7bcee1e..659c9e3b2 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/SimpleMergeTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/merge/SimpleMergeTest.java
@@ -45,7 +45,6 @@
 package org.eclipse.jgit.merge;
 
 import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
-import static org.eclipse.jgit.lib.Constants.OBJ_COMMIT;
 
 import java.io.IOException;
 
@@ -373,7 +372,7 @@ private ObjectId commit(final ObjectInserter odi, final DirCache treeB,
 		c.setCommitter(c.getAuthor());
 		c.setParentIds(parentIds);
 		c.setMessage("Tree " + c.getTreeId().name());
-		ObjectId id = odi.insert(OBJ_COMMIT, odi.format(c));
+		ObjectId id = odi.insert(c);
 		odi.flush();
 		return id;
 	}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/RevCommitParseTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/RevCommitParseTest.java
index 36730c153..7be7dbc81 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/RevCommitParseTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/revwalk/RevCommitParseTest.java
@@ -327,7 +327,7 @@ public void testParse_PublicParseMethod()
 		src.setCommitter(committer);
 		src.setMessage("Test commit\n\nThis is a test.\n");
 
-		RevCommit p = RevCommit.parse(fmt.format(src));
+		RevCommit p = RevCommit.parse(src.format());
 		assertEquals(src.getTreeId(), p.getTree());
 		assertEquals(0, p.getParentCount());
 		assertEquals(author, p.getAuthorIdent());
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 727c48e8e..c694add44 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
@@ -407,7 +407,7 @@ public void testParse_PublicParseMethod() throws CorruptObjectException {
 		src.setTag("a.test");
 		src.setMessage("Test tag\n\nThis is a test.\n");
 
-		RevTag p = RevTag.parse(fmt.format(src));
+		RevTag p = RevTag.parse(src.format());
 		assertEquals(src.getObjectId(), p.getObject());
 		assertEquals(committer, p.getTaggerIdent());
 		assertEquals("a.test", p.getTagName());
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/storage/file/T0003_Basic.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/storage/file/T0003_Basic.java
index cd802d41e..0352a40bf 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/storage/file/T0003_Basic.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/storage/file/T0003_Basic.java
@@ -693,13 +693,12 @@ public void test30_stripWorkDir() {
 
 	}
 
-	private ObjectId insertCommit(final CommitBuilder commit) throws IOException,
+	private ObjectId insertCommit(final CommitBuilder builder) throws IOException,
 			UnsupportedEncodingException {
 		ObjectInserter oi = db.newObjectInserter();
 		try {
-			ObjectId id = oi.insert(Constants.OBJ_COMMIT, oi.format(commit));
+			ObjectId id = oi.insert(builder);
 			oi.flush();
-			commit.setCommitId(id);
 			return id;
 		} finally {
 			oi.release();
@@ -721,9 +720,8 @@ private ObjectId insertTag(final TagBuilder tag) throws IOException,
 			UnsupportedEncodingException {
 		ObjectInserter oi = db.newObjectInserter();
 		try {
-			ObjectId id = oi.insert(Constants.OBJ_TAG, oi.format(tag));
+			ObjectId id = oi.insert(tag);
 			oi.flush();
-			tag.setTagId(id);
 			return id;
 		} finally {
 			oi.release();
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/api/CommitCommand.java b/org.eclipse.jgit/src/org/eclipse/jgit/api/CommitCommand.java
index a88899cc5..e385e7cb8 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/api/CommitCommand.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/api/CommitCommand.java
@@ -169,8 +169,7 @@ public RevCommit call() throws NoHeadException, NoMessageException,
 
 					commit.setParentIds(parents);
 					commit.setTreeId(indexTreeId);
-					ObjectId commitId = odi.insert(Constants.OBJ_COMMIT, odi
-							.format(commit));
+					ObjectId commitId = odi.insert(commit);
 					odi.flush();
 
 					RevWalk revWalk = new RevWalk(repo);
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 8457d4549..8bd02ee29 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/CommitBuilder.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/CommitBuilder.java
@@ -45,6 +45,10 @@
 
 package org.eclipse.jgit.lib;
 
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.OutputStreamWriter;
+import java.io.UnsupportedEncodingException;
 import java.nio.charset.Charset;
 import java.util.List;
 
@@ -62,6 +66,16 @@
 public class CommitBuilder {
 	private static final ObjectId[] EMPTY_OBJECTID_LIST = new ObjectId[0];
 
+	private static final byte[] htree = Constants.encodeASCII("tree");
+
+	private static final byte[] hparent = Constants.encodeASCII("parent");
+
+	private static final byte[] hauthor = Constants.encodeASCII("author");
+
+	private static final byte[] hcommitter = Constants.encodeASCII("committer");
+
+	private static final byte[] hencoding = Constants.encodeASCII("encoding");
+
 	private ObjectId commitId;
 
 	private ObjectId treeId;
@@ -262,6 +276,91 @@ public Charset getEncoding() {
 		return encoding;
 	}
 
+	/**
+	 * Format this builder's state as a commit object.
+	 *
+	 * As a side effect, {@link #getCommitId()} will be populated with the
+	 * proper ObjectId for the formatted content.
+	 *
+	 * @return this object in the canonical commit format, suitable for storage
+	 *         in a repository.
+	 * @throws UnsupportedEncodingException
+	 *             the encoding specified by {@link #getEncoding()} is not
+	 *             supported by this Java runtime.
+	 */
+	public byte[] format() throws UnsupportedEncodingException {
+		return format(new ObjectInserter.Formatter());
+	}
+
+	/**
+	 * Format this builder's state as a commit object.
+	 *
+	 * As a side effect, {@link #getCommitId()} will be populated with the
+	 * proper ObjectId for the formatted content.
+	 *
+	 * @param oi
+	 *            the inserter whose formatting support will be reused. The
+	 *            inserter itself is not affected, and the commit is not
+	 *            actually inserted into the repository.
+	 * @return this object in the canonical commit format, suitable for storage
+	 *         in a repository.
+	 * @throws UnsupportedEncodingException
+	 *             the encoding specified by {@link #getEncoding()} is not
+	 *             supported by this Java runtime.
+	 */
+	public byte[] format(ObjectInserter oi) throws UnsupportedEncodingException {
+		ByteArrayOutputStream os = new ByteArrayOutputStream();
+		OutputStreamWriter w = new OutputStreamWriter(os, getEncoding());
+		try {
+			os.write(htree);
+			os.write(' ');
+			getTreeId().copyTo(os);
+			os.write('\n');
+
+			for (ObjectId p : getParentIds()) {
+				os.write(hparent);
+				os.write(' ');
+				p.copyTo(os);
+				os.write('\n');
+			}
+
+			os.write(hauthor);
+			os.write(' ');
+			w.write(getAuthor().toExternalString());
+			w.flush();
+			os.write('\n');
+
+			os.write(hcommitter);
+			os.write(' ');
+			w.write(getCommitter().toExternalString());
+			w.flush();
+			os.write('\n');
+
+			if (getEncoding() != Constants.CHARSET) {
+				os.write(hencoding);
+				os.write(' ');
+				os.write(Constants.encodeASCII(getEncoding().name()));
+				os.write('\n');
+			}
+
+			os.write('\n');
+
+			if (getMessage() != null) {
+				w.write(getMessage());
+				w.flush();
+			}
+		} catch (IOException err) {
+			// This should never occur, the only way to get it above is
+			// for the ByteArrayOutputStream to throw, but it doesn't.
+			//
+			throw new RuntimeException(err);
+		}
+
+		byte[] content = os.toByteArray();
+		setCommitId(oi.idFor(Constants.OBJ_COMMIT, content));
+		return content;
+	}
+
 	@Override
 	public String toString() {
 		StringBuilder r = new StringBuilder();
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectInserter.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectInserter.java
index 94d792858..102445922 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectInserter.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectInserter.java
@@ -51,9 +51,6 @@
 import java.io.EOFException;
 import java.io.IOException;
 import java.io.InputStream;
-import java.io.OutputStreamWriter;
-import java.io.UnsupportedEncodingException;
-import java.nio.charset.Charset;
 import java.security.MessageDigest;
 import java.text.MessageFormat;
 
@@ -73,16 +70,6 @@
  * otherwise making the returned ObjectIds visible to other code.
  */
 public abstract class ObjectInserter {
-	private static final byte[] htree = Constants.encodeASCII("tree");
-
-	private static final byte[] hparent = Constants.encodeASCII("parent");
-
-	private static final byte[] hauthor = Constants.encodeASCII("author");
-
-	private static final byte[] hcommitter = Constants.encodeASCII("committer");
-
-	private static final byte[] hencoding = Constants.encodeASCII("encoding");
-
 	/** An inserter that can be used for formatting and id generation only. */
 	public static class Formatter extends ObjectInserter {
 		@Override
@@ -194,6 +181,38 @@ public ObjectId idFor(int objectType, long length, InputStream in)
 		return ObjectId.fromRaw(md.digest());
 	}
 
+	/**
+	 * Insert a single commit into the store, returning its unique name.
+	 *
+	 * As a side effect, {@link CommitBuilder#getCommitId()} will also be
+	 * populated with the returned ObjectId.
+	 *
+	 * @param builder
+	 *            the builder containing the proposed commit's data.
+	 * @return the name of the commit object.
+	 * @throws IOException
+	 *             the object could not be stored.
+	 */
+	public final ObjectId insert(CommitBuilder builder) throws IOException {
+		return insert(Constants.OBJ_COMMIT, builder.format(this));
+	}
+
+	/**
+	 * Insert a single annotated tag into the store, returning its unique name.
+	 *
+	 * As a side effect, {@link TagBuilder#getTagId()} will also be populated
+	 * with the returned ObjectId.
+	 *
+	 * @param builder
+	 *            the builder containing the proposed tag's data.
+	 * @return the name of the tag object.
+	 * @throws IOException
+	 *             the object could not be stored.
+	 */
+	public final ObjectId insert(TagBuilder builder) throws IOException {
+		return insert(Constants.OBJ_TAG, builder.format(this));
+	}
+
 	/**
 	 * Insert a single object into the store, returning its unique name.
 	 *
@@ -293,107 +312,4 @@ public final byte[] format(Tree tree) throws IOException {
 		}
 		return o.toByteArray();
 	}
-
-	/**
-	 * Format a Commit in canonical format.
-	 *
-	 * @param commit
-	 *            the commit object to format
-	 * @return canonical encoding of the commit object.
-	 * @throws UnsupportedEncodingException
-	 *             the commit's chosen encoding isn't supported on this JVM.
-	 */
-	public final byte[] format(CommitBuilder commit)
-			throws UnsupportedEncodingException {
-		Charset encoding = commit.getEncoding();
-		ByteArrayOutputStream os = new ByteArrayOutputStream();
-		OutputStreamWriter w = new OutputStreamWriter(os, encoding);
-		try {
-			os.write(htree);
-			os.write(' ');
-			commit.getTreeId().copyTo(os);
-			os.write('\n');
-
-			for (ObjectId p : commit.getParentIds()) {
-				os.write(hparent);
-				os.write(' ');
-				p.copyTo(os);
-				os.write('\n');
-			}
-
-			os.write(hauthor);
-			os.write(' ');
-			w.write(commit.getAuthor().toExternalString());
-			w.flush();
-			os.write('\n');
-
-			os.write(hcommitter);
-			os.write(' ');
-			w.write(commit.getCommitter().toExternalString());
-			w.flush();
-			os.write('\n');
-
-			if (encoding != Constants.CHARSET) {
-				os.write(hencoding);
-				os.write(' ');
-				os.write(Constants.encodeASCII(encoding.name()));
-				os.write('\n');
-			}
-
-			os.write('\n');
-
-			if (commit.getMessage() != null) {
-				w.write(commit.getMessage());
-				w.flush();
-			}
-		} catch (IOException err) {
-			// This should never occur, the only way to get it above is
-			// for the ByteArrayOutputStream to throw, but it doesn't.
-			//
-			throw new RuntimeException(err);
-		}
-		return os.toByteArray();
-	}
-
-	/**
-	 * Format a Tag in canonical format.
-	 *
-	 * @param tag
-	 *            the tag object to format
-	 * @return canonical encoding of the tag object.
-	 */
-	public final byte[] format(TagBuilder tag) {
-		ByteArrayOutputStream os = new ByteArrayOutputStream();
-		OutputStreamWriter w = new OutputStreamWriter(os, Constants.CHARSET);
-		try {
-			w.write("object ");
-			tag.getObjectId().copyTo(w);
-			w.write('\n');
-
-			w.write("type ");
-			w.write(Constants.typeString(tag.getObjectType()));
-			w.write("\n");
-
-			w.write("tag ");
-			w.write(tag.getTag());
-			w.write("\n");
-
-			if (tag.getTagger() != null) {
-				w.write("tagger ");
-				w.write(tag.getTagger().toExternalString());
-				w.write('\n');
-			}
-
-			w.write('\n');
-			if (tag.getMessage() != null)
-				w.write(tag.getMessage());
-			w.close();
-		} catch (IOException err) {
-			// This should never occur, the only way to get it above is
-			// for the ByteArrayOutputStream to throw, but it doesn't.
-			//
-			throw new RuntimeException(err);
-		}
-		return os.toByteArray();
-	}
 }
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectWriter.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectWriter.java
index 5cb4b2168..339986be0 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectWriter.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectWriter.java
@@ -46,8 +46,6 @@
 package org.eclipse.jgit.lib;
 
 import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
-import static org.eclipse.jgit.lib.Constants.OBJ_COMMIT;
-import static org.eclipse.jgit.lib.Constants.OBJ_TAG;
 import static org.eclipse.jgit.lib.Constants.OBJ_TREE;
 
 import java.io.File;
@@ -174,7 +172,7 @@ public ObjectId writeCanonicalTree(byte[] treeData) throws IOException {
 	 */
 	public ObjectId writeCommit(CommitBuilder commit) throws IOException {
 		try {
-			ObjectId id = inserter.insert(OBJ_COMMIT, inserter.format(commit));
+			ObjectId id = inserter.insert(commit);
 			inserter.flush();
 			return id;
 		} finally {
@@ -192,7 +190,7 @@ public ObjectId writeCommit(CommitBuilder commit) throws IOException {
 	 */
 	public ObjectId writeTag(TagBuilder tag) throws IOException {
 		try {
-			ObjectId id = inserter.insert(OBJ_TAG, inserter.format(tag));
+			ObjectId id = inserter.insert(tag);
 			inserter.flush();
 			return id;
 		} finally {
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 6cd0e9e88..71e46494c 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/TagBuilder.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/TagBuilder.java
@@ -45,6 +45,10 @@
 
 package org.eclipse.jgit.lib;
 
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.OutputStreamWriter;
+
 import org.eclipse.jgit.revwalk.RevObject;
 
 /**
@@ -169,6 +173,70 @@ public void setMessage(final String newMessage) {
 		tagId = null;
 	}
 
+	/**
+	 * Format this builder's state as an annotated tag object.
+	 *
+	 * As a side effect, {@link #getTagId()} will be populated with the proper
+	 * ObjectId for the formatted content.
+	 *
+	 * @return this object in the canonical annotated tag format, suitable for
+	 *         storage in a repository.
+	 */
+	public byte[] format() {
+		return format(new ObjectInserter.Formatter());
+	}
+
+	/**
+	 * Format this builder's state as an annotated tag object.
+	 *
+	 * As a side effect, {@link #getTagId()} will be populated with the proper
+	 * ObjectId for the formatted content.
+	 *
+	 * @param oi
+	 *            the inserter whose formatting support will be reused. The
+	 *            inserter itself is not affected, and the annotated tag is not
+	 *            actually inserted into the repository.
+	 * @return this object in the canonical annotated tag format, suitable for
+	 *         storage in a repository.
+	 */
+	public byte[] format(ObjectInserter oi) {
+		ByteArrayOutputStream os = new ByteArrayOutputStream();
+		OutputStreamWriter w = new OutputStreamWriter(os, Constants.CHARSET);
+		try {
+			w.write("object ");
+			getObjectId().copyTo(w);
+			w.write('\n');
+
+			w.write("type ");
+			w.write(Constants.typeString(getObjectType()));
+			w.write("\n");
+
+			w.write("tag ");
+			w.write(getTag());
+			w.write("\n");
+
+			if (getTagger() != null) {
+				w.write("tagger ");
+				w.write(getTagger().toExternalString());
+				w.write('\n');
+			}
+
+			w.write('\n');
+			if (getMessage() != null)
+				w.write(getMessage());
+			w.close();
+		} catch (IOException err) {
+			// This should never occur, the only way to get it above is
+			// for the ByteArrayOutputStream to throw, but it doesn't.
+			//
+			throw new RuntimeException(err);
+		}
+
+		byte[] content = os.toByteArray();
+		setTagId(oi.idFor(Constants.OBJ_TAG, content));
+		return content;
+	}
+
 	@Override
 	public String toString() {
 		StringBuilder r = new StringBuilder();