Merge changes from topic 'update-index-ref-decorator'

* changes:
  RefCursor: Remove unnecessary getUpdateIndex method
  RefDatabase/Ref: Add versioning to reference database

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/RefDirectoryTest.java

@@ -61,6 +61,7 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.List;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicReference;
@@ -134,6 +135,33 @@ public void testCreate() throws IOException {
 		assertEquals("ref: refs/heads/master\n", read(new File(d, HEAD)));
 	}
 
+	@Test(expected = UnsupportedOperationException.class)
+	public void testVersioningNotImplemented_exactRef() throws IOException {
+		assertFalse(refdir.hasVersioning());
+
+		Ref ref = refdir.exactRef(HEAD);
+		assertNotNull(ref);
+		ref.getUpdateIndex(); // Not implemented on FS
+	}
+
+	@Test
+	public void testVersioningNotImplemented_getRefs() throws Exception {
+		assertFalse(refdir.hasVersioning());
+
+		RevCommit C = repo.commit().parent(B).create();
+		repo.update("master", C);
+		List<Ref> refs = refdir.getRefs();
+
+		for (Ref ref : refs) {
+			try {
+				ref.getUpdateIndex();
+				fail("FS doesn't implement ref versioning");
+			} catch (UnsupportedOperationException e) {
+				// ok
+			}
+		}
+	}
+
 	@Test
 	public void testGetRefs_EmptyDatabase() throws IOException {
 		Map<String, Ref> all;

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/MergedReftableTest.java

@@ -44,6 +44,7 @@
 package org.eclipse.jgit.internal.storage.reftable;
 
 import static org.eclipse.jgit.lib.Constants.HEAD;
+import static org.eclipse.jgit.lib.Constants.MASTER;
 import static org.eclipse.jgit.lib.Constants.OBJECT_ID_LENGTH;
 import static org.eclipse.jgit.lib.Constants.R_HEADS;
 import static org.eclipse.jgit.lib.Ref.Storage.NEW;
@@ -68,6 +69,7 @@
 import org.eclipse.jgit.lib.ObjectIdRef;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.RefComparator;
+import org.eclipse.jgit.lib.SymbolicRef;
 import org.junit.Test;
 
 public class MergedReftableTest {
@@ -128,6 +130,7 @@ public void oneTableScan() throws IOException {
 				Ref act = rc.getRef();
 				assertEquals(exp.getName(), act.getName());
 				assertEquals(exp.getObjectId(), act.getObjectId());
+				assertEquals(1, act.getUpdateIndex());
 			}
 			assertFalse(rc.next());
 		}
@@ -145,6 +148,7 @@ public void deleteIsHidden() throws IOException {
 			assertTrue(rc.next());
 			assertEquals("refs/heads/master", rc.getRef().getName());
 			assertEquals(id(2), rc.getRef().getObjectId());
+			assertEquals(1, rc.getRef().getUpdateIndex());
 			assertFalse(rc.next());
 		}
 	}
@@ -162,6 +166,7 @@ public void twoTableSeek() throws IOException {
 			assertEquals("refs/heads/master", rc.getRef().getName());
 			assertEquals(id(2), rc.getRef().getObjectId());
 			assertFalse(rc.next());
+			assertEquals(1, rc.getRef().getUpdateIndex());
 		}
 	}
 
@@ -177,6 +182,7 @@ public void twoTableById() throws IOException {
 			assertTrue(rc.next());
 			assertEquals("refs/heads/master", rc.getRef().getName());
 			assertEquals(id(2), rc.getRef().getObjectId());
+			assertEquals(1, rc.getRef().getUpdateIndex());
 			assertFalse(rc.next());
 		}
 	}
@@ -212,6 +218,7 @@ public void fourTableScan() throws IOException {
 				Ref act = rc.getRef();
 				assertEquals(exp.getName(), act.getName());
 				assertEquals(exp.getObjectId(), act.getObjectId());
+				assertEquals(1, rc.getRef().getUpdateIndex());
 			}
 			assertFalse(rc.next());
 		}
@@ -231,9 +238,11 @@ public void scanDuplicates() throws IOException {
 			assertTrue(rc.next());
 			assertEquals("refs/heads/apple", rc.getRef().getName());
 			assertEquals(id(3), rc.getRef().getObjectId());
+			assertEquals(2000, rc.getRef().getUpdateIndex());
 			assertTrue(rc.next());
 			assertEquals("refs/heads/banana", rc.getRef().getName());
 			assertEquals(id(2), rc.getRef().getObjectId());
+			assertEquals(1000, rc.getRef().getUpdateIndex());
 			assertFalse(rc.next());
 		}
 	}
@@ -251,12 +260,14 @@ public void scanIncludeDeletes() throws IOException {
 			Ref r = rc.getRef();
 			assertEquals("refs/heads/master", r.getName());
 			assertEquals(id(8), r.getObjectId());
+			assertEquals(1, rc.getRef().getUpdateIndex());
 
 			assertTrue(rc.next());
 			r = rc.getRef();
 			assertEquals("refs/heads/next", r.getName());
 			assertEquals(NEW, r.getStorage());
 			assertNull(r.getObjectId());
+			assertEquals(1, rc.getRef().getUpdateIndex());
 
 			assertFalse(rc.next());
 		}
@@ -277,6 +288,7 @@ public void oneTableSeek() throws IOException {
 				Ref act = rc.getRef();
 				assertEquals(exp.getName(), act.getName());
 				assertEquals(exp.getObjectId(), act.getObjectId());
+				assertEquals(1, act.getUpdateIndex());
 				assertFalse(rc.next());
 			}
 		}
@@ -303,17 +315,17 @@ public void missedUpdate() throws IOException {
 			assertTrue(rc.next());
 			assertEquals("refs/heads/a", rc.getRef().getName());
 			assertEquals(id(1), rc.getRef().getObjectId());
-			assertEquals(1, rc.getUpdateIndex());
+			assertEquals(1, rc.getRef().getUpdateIndex());
 
 			assertTrue(rc.next());
 			assertEquals("refs/heads/b", rc.getRef().getName());
 			assertEquals(id(2), rc.getRef().getObjectId());
-			assertEquals(2, rc.getUpdateIndex());
+			assertEquals(2, rc.getRef().getUpdateIndex());
 
 			assertTrue(rc.next());
 			assertEquals("refs/heads/c", rc.getRef().getName());
 			assertEquals(id(3), rc.getRef().getObjectId());
-			assertEquals(3, rc.getUpdateIndex());
+			assertEquals(3, rc.getRef().getUpdateIndex());
 		}
 	}
 
@@ -344,6 +356,63 @@ public void compaction() throws IOException {
 		}
 	}
 
+	@Test
+	public void versioningSymbolicReftargetMoves() throws IOException {
+		Ref master = ref(MASTER, 100);
+
+		List<Ref> delta1 = Arrays.asList(master, sym(HEAD, MASTER));
+		List<Ref> delta2 = Arrays.asList(ref(MASTER, 200));
+
+		MergedReftable mr = merge(write(delta1, 1), write(delta2, 2));
+		Ref head = mr.exactRef(HEAD);
+		assertEquals(head.getUpdateIndex(), 1);
+
+		Ref masterRef = mr.exactRef(MASTER);
+		assertEquals(masterRef.getUpdateIndex(), 2);
+	}
+
+	@Test
+	public void versioningSymbolicRefMoves() throws IOException {
+		Ref branchX = ref("refs/heads/branchX", 200);
+
+		List<Ref> delta1 = Arrays.asList(ref(MASTER, 100), branchX,
+				sym(HEAD, MASTER));
+		List<Ref> delta2 = Arrays.asList(sym(HEAD, "refs/heads/branchX"));
+		List<Ref> delta3 = Arrays.asList(sym(HEAD, MASTER));
+
+		MergedReftable mr = merge(write(delta1, 1), write(delta2, 2),
+				write(delta3, 3));
+		Ref head = mr.exactRef(HEAD);
+		assertEquals(head.getUpdateIndex(), 3);
+
+		Ref masterRef = mr.exactRef(MASTER);
+		assertEquals(masterRef.getUpdateIndex(), 1);
+
+		Ref branchRef = mr.exactRef(MASTER);
+		assertEquals(branchRef.getUpdateIndex(), 1);
+	}
+
+	@Test
+	public void versioningResolveRef() throws IOException {
+		List<Ref> delta1 = Arrays.asList(sym(HEAD, "refs/heads/tmp"),
+				sym("refs/heads/tmp", MASTER), ref(MASTER, 100));
+		List<Ref> delta2 = Arrays.asList(ref(MASTER, 200));
+		List<Ref> delta3 = Arrays.asList(ref(MASTER, 300));
+
+		MergedReftable mr = merge(write(delta1, 1), write(delta2, 2),
+				write(delta3, 3));
+		Ref head = mr.exactRef(HEAD);
+		Ref resolvedHead = mr.resolve(head);
+		assertEquals(resolvedHead.getObjectId(), id(300));
+		assertEquals("HEAD has not moved", resolvedHead.getUpdateIndex(), 1);
+
+		Ref master = mr.exactRef(MASTER);
+		Ref resolvedMaster = mr.resolve(master);
+		assertEquals(resolvedMaster.getObjectId(), id(300));
+		assertEquals("master also has update index",
+				resolvedMaster.getUpdateIndex(), 3);
+	}
+
 	private static MergedReftable merge(byte[]... table) {
 		List<Reftable> stack = new ArrayList<>(table.length);
 		for (byte[] b : table) {
@@ -360,6 +429,14 @@ private static Ref ref(String name, int id) {
 		return new ObjectIdRef.PeeledNonTag(PACKED, name, id(id));
 	}
 
+	private static Ref sym(String name, String target) {
+		return new SymbolicRef(name, newRef(target));
+	}
+
+	private static Ref newRef(String name) {
+		return new ObjectIdRef.Unpeeled(NEW, name, null);
+	}
+
 	private static Ref delete(String name) {
 		return new ObjectIdRef.Unpeeled(NEW, name, null);
 	}

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/ReftableCompactorTest.java

@@ -108,7 +108,7 @@ public void oneTable() throws IOException {
 			assertTrue(rc.next());
 			assertEquals(MASTER, rc.getRef().getName());
 			assertEquals(id(1), rc.getRef().getObjectId());
-			assertEquals(0, rc.getUpdateIndex());
+			assertEquals(0, rc.getRef().getUpdateIndex());
 		}
 	}
 
@@ -155,7 +155,7 @@ public void twoTablesOneRef() throws IOException {
 			assertTrue(rc.next());
 			assertEquals(MASTER, rc.getRef().getName());
 			assertEquals(id(2), rc.getRef().getObjectId());
-			assertEquals(1, rc.getUpdateIndex());
+			assertEquals(1, rc.getRef().getUpdateIndex());
 		}
 	}
 
@@ -203,12 +203,12 @@ public void twoTablesTwoRefs() throws IOException {
 			assertTrue(rc.next());
 			assertEquals(MASTER, rc.getRef().getName());
 			assertEquals(id(3), rc.getRef().getObjectId());
-			assertEquals(1, rc.getUpdateIndex());
+			assertEquals(1, rc.getRef().getUpdateIndex());
 
 			assertTrue(rc.next());
 			assertEquals(NEXT, rc.getRef().getName());
 			assertEquals(id(2), rc.getRef().getObjectId());
-			assertEquals(0, rc.getUpdateIndex());
+			assertEquals(0, rc.getRef().getUpdateIndex());
 		}
 	}
 

org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/reftable/ReftableTest.java

@@ -186,6 +186,7 @@ public void oneIdRef() throws IOException {
 			assertFalse(act.isSymbolic());
 			assertEquals(exp.getName(), act.getName());
 			assertEquals(exp.getObjectId(), act.getObjectId());
+			assertEquals(0, act.getUpdateIndex());
 			assertNull(act.getPeeledObjectId());
 			assertFalse(rc.wasDeleted());
 			assertFalse(rc.next());
@@ -195,6 +196,7 @@ public void oneIdRef() throws IOException {
 			Ref act = rc.getRef();
 			assertNotNull(act);
 			assertEquals(exp.getName(), act.getName());
+			assertEquals(0, act.getUpdateIndex());
 			assertFalse(rc.next());
 		}
 	}
@@ -216,6 +218,7 @@ public void oneTagRef() throws IOException {
 			assertEquals(exp.getName(), act.getName());
 			assertEquals(exp.getObjectId(), act.getObjectId());
 			assertEquals(exp.getPeeledObjectId(), act.getPeeledObjectId());
+			assertEquals(0, act.getUpdateIndex());
 		}
 	}
 
@@ -237,6 +240,7 @@ public void oneSymbolicRef() throws IOException {
 			assertNotNull(act.getLeaf());
 			assertEquals(MASTER, act.getTarget().getName());
 			assertNull(act.getObjectId());
+			assertEquals(0, act.getUpdateIndex());
 		}
 	}
 
@@ -250,14 +254,17 @@ public void resolveSymbolicRef() throws IOException {
 		Ref head = t.exactRef(HEAD);
 		assertNull(head.getObjectId());
 		assertEquals("refs/heads/tmp", head.getTarget().getName());
+		assertEquals(0, head.getUpdateIndex());
 
 		head = t.resolve(head);
 		assertNotNull(head);
 		assertEquals(id(1), head.getObjectId());
+		assertEquals(0, head.getUpdateIndex());
 
 		Ref master = t.exactRef(MASTER);
 		assertNotNull(master);
 		assertSame(master, t.resolve(master));
+		assertEquals(0, master.getUpdateIndex());
 	}
 
 	@Test
@@ -335,14 +342,17 @@ public void namespaceHeads() throws IOException {
 		try (RefCursor rc = t.seekRefsWithPrefix("refs/tags/")) {
 			assertTrue(rc.next());
 			assertEquals(V1_0, rc.getRef().getName());
+			assertEquals(0, rc.getRef().getUpdateIndex());
 			assertFalse(rc.next());
 		}
 		try (RefCursor rc = t.seekRefsWithPrefix("refs/heads/")) {
 			assertTrue(rc.next());
 			assertEquals(MASTER, rc.getRef().getName());
+			assertEquals(0, rc.getRef().getUpdateIndex());
 
 			assertTrue(rc.next());
 			assertEquals(NEXT, rc.getRef().getName());
+			assertEquals(0, rc.getRef().getUpdateIndex());
 
 			assertFalse(rc.next());
 		}
@@ -432,11 +442,12 @@ public void withReflog() throws IOException {
 			assertTrue(rc.next());
 			assertEquals(MASTER, rc.getRef().getName());
 			assertEquals(id(1), rc.getRef().getObjectId());
-			assertEquals(1, rc.getUpdateIndex());
+			assertEquals(1, rc.getRef().getUpdateIndex());
 
 			assertTrue(rc.next());
 			assertEquals(NEXT, rc.getRef().getName());
 			assertEquals(id(2), rc.getRef().getObjectId());
+			assertEquals(1, rc.getRef().getUpdateIndex());
 			assertFalse(rc.next());
 		}
 		try (LogCursor lc = t.allLogs()) {
@@ -569,6 +580,7 @@ public void byObjectIdOneRefNoIndex() throws IOException {
 			assertTrue("has 42", rc.next());
 			assertEquals("refs/heads/42", rc.getRef().getName());
 			assertEquals(id(42), rc.getRef().getObjectId());
+			assertEquals(0, rc.getRef().getUpdateIndex());
 			assertFalse(rc.next());
 		}
 		try (RefCursor rc = t.byObjectId(id(100))) {
@@ -579,6 +591,7 @@ public void byObjectIdOneRefNoIndex() throws IOException {
 			assertTrue("has master", rc.next());
 			assertEquals("refs/heads/master", rc.getRef().getName());
 			assertEquals(id(100), rc.getRef().getObjectId());
+			assertEquals(0, rc.getRef().getUpdateIndex());
 
 			assertFalse(rc.next());
 		}
@@ -600,6 +613,7 @@ public void byObjectIdOneRefWithIndex() throws IOException {
 			assertTrue("has 42", rc.next());
 			assertEquals("refs/heads/42", rc.getRef().getName());
 			assertEquals(id(42), rc.getRef().getObjectId());
+			assertEquals(0, rc.getRef().getUpdateIndex());
 			assertFalse(rc.next());
 		}
 		try (RefCursor rc = t.byObjectId(id(100))) {
@@ -610,6 +624,7 @@ public void byObjectIdOneRefWithIndex() throws IOException {
 			assertTrue("has master", rc.next());
 			assertEquals("refs/heads/master", rc.getRef().getName());
 			assertEquals(id(100), rc.getRef().getObjectId());
+			assertEquals(0, rc.getRef().getUpdateIndex());
 
 			assertFalse(rc.next());
 		}
@@ -654,7 +669,6 @@ public void badCrc32() throws IOException {
 		}
 	}
 
-
 	private static void assertScan(List<Ref> refs, Reftable t)
 			throws IOException {
 		try (RefCursor rc = t.allRefs()) {
@@ -663,6 +677,7 @@ private static void assertScan(List<Ref> refs, Reftable t)
 				Ref act = rc.getRef();
 				assertEquals(exp.getName(), act.getName());
 				assertEquals(exp.getObjectId(), act.getObjectId());
+				assertEquals(0, rc.getRef().getUpdateIndex());
 			}
 			assertFalse(rc.next());
 		}
@@ -676,6 +691,7 @@ private static void assertSeek(List<Ref> refs, Reftable t)
 				Ref act = rc.getRef();
 				assertEquals(exp.getName(), act.getName());
 				assertEquals(exp.getObjectId(), act.getObjectId());
+				assertEquals(0, rc.getRef().getUpdateIndex());
 				assertFalse(rc.next());
 			}
 		}

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/ObjectIdRefTest.java

@@ -48,6 +48,10 @@
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+import java.util.Arrays;
+import java.util.List;
 
 import org.junit.Test;
 
@@ -114,11 +118,44 @@ public void testConstructor_Peeled() {
 		assertSame(ID_B, r.getPeeledObjectId());
 	}
 
+	@Test
+	public void testUpdateIndex() {
+		ObjectIdRef r;
+
+		r = new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE, name, ID_A, 3);
+		assertTrue(r.getUpdateIndex() == 3);
+
+		r = new ObjectIdRef.PeeledTag(Ref.Storage.LOOSE, name, ID_A, ID_B, 4);
+		assertTrue(r.getUpdateIndex() == 4);
+
+		r = new ObjectIdRef.PeeledNonTag(Ref.Storage.LOOSE, name, ID_A, 5);
+		assertTrue(r.getUpdateIndex() == 5);
+	}
+
+	@Test
+	public void testUpdateIndexNotSet() {
+		List<ObjectIdRef> r = Arrays.asList(
+				new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE, name, ID_A),
+				new ObjectIdRef.PeeledTag(Ref.Storage.LOOSE, name, ID_A, ID_B),
+				new ObjectIdRef.PeeledNonTag(Ref.Storage.LOOSE, name, ID_A));
+
+		for (ObjectIdRef ref : r) {
+			try {
+				ref.getUpdateIndex();
+				fail("Update index wasn't set. It must throw");
+			} catch (UnsupportedOperationException u) {
+				// Ok
+			}
+		}
+	}
+
+
 	@Test
 	public void testToString() {
 		ObjectIdRef r;
 
 		r = new ObjectIdRef.Unpeeled(Ref.Storage.LOOSE, name, ID_A);
-		assertEquals("Ref[" + name + "=" + ID_A.name() + "]", r.toString());
+		assertEquals("Ref[" + name + "=" + ID_A.name() + "(-1)]",
+				r.toString());
 	}
 }

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/SymbolicRefTest.java

@@ -68,7 +68,7 @@ public void testConstructor() {
 		SymbolicRef r;
 
 		t = new ObjectIdRef.Unpeeled(Ref.Storage.NEW, targetName, null);
-		r = new SymbolicRef(name, t);
+		r = new SymbolicRef(name, t, 1);
 		assertSame(Ref.Storage.LOOSE, r.getStorage());
 		assertSame(name, r.getName());
 		assertNull("no id on new ref", r.getObjectId());
@@ -77,9 +77,10 @@ public void testConstructor() {
 		assertSame("leaf is t", t, r.getLeaf());
 		assertSame("target is t", t, r.getTarget());
 		assertTrue("is symbolic", r.isSymbolic());
+		assertTrue("holds update index", r.getUpdateIndex() == 1);
 
 		t = new ObjectIdRef.Unpeeled(Ref.Storage.PACKED, targetName, ID_A);
-		r = new SymbolicRef(name, t);
+		r = new SymbolicRef(name, t, 2);
 		assertSame(Ref.Storage.LOOSE, r.getStorage());
 		assertSame(name, r.getName());
 		assertSame(ID_A, r.getObjectId());
@@ -88,6 +89,7 @@ public void testConstructor() {
 		assertSame("leaf is t", t, r.getLeaf());
 		assertSame("target is t", t, r.getTarget());
 		assertTrue("is symbolic", r.isSymbolic());
+		assertTrue("holds update index", r.getUpdateIndex() == 2);
 	}
 
 	@Test
@@ -133,6 +135,6 @@ public void testToString() {
 		d = new SymbolicRef("D", c);
 
 		assertEquals("SymbolicRef[D -> C -> B -> " + targetName + "="
-				+ ID_A.name() + "]", d.toString());
+				+ ID_A.name() + "(-1)]", d.toString());
 	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsReftableDatabase.java

@@ -97,6 +97,12 @@ protected DfsReftableDatabase(DfsRepository repo) {
 		super(repo);
 	}
 
+	/** {@inheritDoc} */
+	@Override
+	public boolean hasVersioning() {
+		return true;
+	}
+
 	/** {@inheritDoc} */
 	@Override
 	public boolean performsAtomicTransactions() {

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/BlockReader.java

@@ -170,24 +170,27 @@ long readUpdateIndexDelta() {
 		return readVarint64();
 	}
 
-	Ref readRef() throws IOException {
+	Ref readRef(long minUpdateIndex) throws IOException {
+		long updateIndex = minUpdateIndex + readUpdateIndexDelta();
 		String name = RawParseUtils.decode(UTF_8, nameBuf, 0, nameLen);
 		switch (valueType & VALUE_TYPE_MASK) {
 		case VALUE_NONE: // delete
-			return newRef(name);
+			return newRef(name, updateIndex);
 
 		case VALUE_1ID:
-			return new ObjectIdRef.PeeledNonTag(PACKED, name, readValueId());
+			return new ObjectIdRef.PeeledNonTag(PACKED, name, readValueId(),
+					updateIndex);
 
 		case VALUE_2ID: { // annotated tag
 			ObjectId id1 = readValueId();
 			ObjectId id2 = readValueId();
-			return new ObjectIdRef.PeeledTag(PACKED, name, id1, id2);
+			return new ObjectIdRef.PeeledTag(PACKED, name, id1, id2,
+					updateIndex);
 		}
 
 		case VALUE_SYMREF: {
 			String val = readValueString();
-			return new SymbolicRef(name, newRef(val));
+			return new SymbolicRef(name, newRef(val, updateIndex), updateIndex);
 		}
 
 		default:
@@ -410,7 +413,7 @@ void verifyIndex() throws IOException {
 	 * <ul>
 	 * <li>{@link #name()}
 	 * <li>{@link #match(byte[], boolean)}
-	 * <li>{@link #readRef()}
+	 * <li>{@link #readRef(long)}
 	 * <li>{@link #readLogUpdateIndex()}
 	 * <li>{@link #readLogEntry()}
 	 * <li>{@link #readBlockPositionList()}
@@ -575,8 +578,8 @@ private long readVarint64() {
 		return val;
 	}
 
-	private static Ref newRef(String name) {
+	private static Ref newRef(String name, long updateIndex) {
-		return new ObjectIdRef.Unpeeled(NEW, name, null);
+		return new ObjectIdRef.Unpeeled(NEW, name, null, updateIndex);
 	}
 
 	private static IOException invalidBlock() {

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/MergedReftable.java

@@ -168,7 +168,6 @@ private class MergedRefCursor extends RefCursor {
 		private final PriorityQueue<RefQueueEntry> queue;
 		private RefQueueEntry head;
 		private Ref ref;
-		private long updateIndex;
 
 		MergedRefCursor() {
 			queue = new PriorityQueue<>(queueSize(), RefQueueEntry::compare);
@@ -206,7 +205,6 @@ public boolean next() throws IOException {
 				}
 
 				ref = t.rc.getRef();
-				updateIndex = t.rc.getUpdateIndex();
 				boolean include = includeDeletes || !t.rc.wasDeleted();
 				add(t);
 				skipShadowedRefs(ref.getName());
@@ -241,11 +239,6 @@ public Ref getRef() {
 			return ref;
 		}
 
-		@Override
-		public long getUpdateIndex() {
-			return updateIndex;
-		}
-
 		@Override
 		public void close() {
 			if (head != null) {
@@ -285,7 +278,7 @@ String name() {
 		}
 
 		long updateIndex() {
-			return rc.getUpdateIndex();
+			return rc.getRef().getUpdateIndex();
 		}
 	}
 

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/RefCursor.java

@@ -68,13 +68,6 @@ public abstract class RefCursor implements AutoCloseable {
 	 */
 	public abstract Ref getRef();
 
-	/**
-	 * Get updateIndex that last modified the current reference.
-	 *
-	 * @return updateIndex that last modified the current reference.
-	 */
-	public abstract long getUpdateIndex();
-
 	/**
 	 * Whether the current reference was deleted.
 	 *

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/Reftable.java

@@ -280,7 +280,7 @@ private Ref resolve(Ref ref, int depth) throws IOException {
 		if (dst == null) {
 			return null; // claim it doesn't exist
 		}
-		return new SymbolicRef(ref.getName(), dst);
+		return new SymbolicRef(ref.getName(), dst, ref.getUpdateIndex());
 	}
 
 	/** {@inheritDoc} */

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableCompactor.java

@@ -256,7 +256,7 @@ public Stats getStats() {
 	private void mergeRefs(MergedReftable mr) throws IOException {
 		try (RefCursor rc = mr.allRefs()) {
 			while (rc.next()) {
-				writer.writeRef(rc.getRef(), rc.getUpdateIndex());
+				writer.writeRef(rc.getRef(), rc.getRef().getUpdateIndex());
 			}
 		}
 	}

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/reftable/ReftableReader.java

@@ -479,7 +479,6 @@ private class RefCursorImpl extends RefCursor {
 		private final boolean prefix;
 
 		private Ref ref;
-		private long updateIndex;
 		BlockReader block;
 
 		RefCursorImpl(long scanEnd, byte[] match, boolean prefix) {
@@ -508,8 +507,7 @@ public boolean next() throws IOException {
 					return false;
 				}
 
-				updateIndex = minUpdateIndex + block.readUpdateIndexDelta();
+				ref = block.readRef(minUpdateIndex);
-				ref = block.readRef();
 				if (!includeDeletes && wasDeleted()) {
 					continue;
 				}
@@ -522,11 +520,6 @@ public Ref getRef() {
 			return ref;
 		}
 
-		@Override
-		public long getUpdateIndex() {
-			return updateIndex;
-		}
-
 		@Override
 		public void close() {
 			// Do nothing.
@@ -605,7 +598,6 @@ private class ObjCursorImpl extends RefCursor {
 		private final ObjectId match;
 
 		private Ref ref;
-		private long updateIndex;
 		private int listIdx;
 
 		private LongList blockPos;
@@ -679,8 +671,7 @@ public boolean next() throws IOException {
 				}
 
 				block.parseKey();
-				updateIndex = minUpdateIndex + block.readUpdateIndexDelta();
+				ref = block.readRef(minUpdateIndex);
-				ref = block.readRef();
 				ObjectId id = ref.getObjectId();
 				if (id != null && match.equals(id)
 						&& (includeDeletes || !wasDeleted())) {
@@ -694,11 +685,6 @@ public Ref getRef() {
 			return ref;
 		}
 
-		@Override
-		public long getUpdateIndex() {
-			return updateIndex;
-		}
-
 		@Override
 		public void close() {
 			// Do nothing.

org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectIdRef.java

@@ -67,7 +67,25 @@ public static class Unpeeled extends ObjectIdRef {
 		 */
 		public Unpeeled(@NonNull Storage st, @NonNull String name,
 				@Nullable ObjectId id) {
-			super(st, name, id);
+			super(st, name, id, -1);
+		}
+
+		/**
+		 * Create a new ref pairing with update index.
+		 *
+		 * @param st
+		 *            method used to store this ref.
+		 * @param name
+		 *            name of this ref.
+		 * @param id
+		 *            current value of the ref. May be {@code null} to indicate
+		 *            a ref that does not exist yet.
+		 * @param updateIndex
+		 *            number increasing with each update to the reference.
+		 */
+		public Unpeeled(@NonNull Storage st, @NonNull String name,
+				@Nullable ObjectId id, long updateIndex) {
+			super(st, name, id, updateIndex);
 		}
 
 		@Override
@@ -100,7 +118,28 @@ public static class PeeledTag extends ObjectIdRef {
 		 */
 		public PeeledTag(@NonNull Storage st, @NonNull String name,
 				@Nullable ObjectId id, @NonNull ObjectId p) {
-			super(st, name, id);
+			super(st, name, id, -1);
+			peeledObjectId = p;
+		}
+
+		/**
+		 * Create a new ref pairing with update index.
+		 *
+		 * @param st
+		 *            method used to store this ref.
+		 * @param name
+		 *            name of this ref.
+		 * @param id
+		 *            current value of the ref. May be {@code null} to indicate
+		 *            a ref that does not exist yet.
+		 * @param p
+		 *            the first non-tag object that tag {@code id} points to.
+		 * @param updateIndex
+		 *            number increasing with each update to the reference.
+		 */
+		public PeeledTag(@NonNull Storage st, @NonNull String name,
+				@Nullable ObjectId id, @NonNull ObjectId p, long updateIndex) {
+			super(st, name, id, updateIndex);
 			peeledObjectId = p;
 		}
 
@@ -131,7 +170,25 @@ public static class PeeledNonTag extends ObjectIdRef {
 		 */
 		public PeeledNonTag(@NonNull Storage st, @NonNull String name,
 				@Nullable ObjectId id) {
-			super(st, name, id);
+			super(st, name, id, -1);
+		}
+
+		/**
+		 * Create a new ref pairing with update index.
+		 *
+		 * @param st
+		 *            method used to store this ref.
+		 * @param name
+		 *            name of this ref.
+		 * @param id
+		 *            current value of the ref. May be {@code null} to indicate
+		 *            a ref that does not exist yet.
+		 * @param updateIndex
+		 *            number increasing with each update to the reference.
+		 */
+		public PeeledNonTag(@NonNull Storage st, @NonNull String name,
+				@Nullable ObjectId id, long updateIndex) {
+			super(st, name, id, updateIndex);
 		}
 
 		@Override
@@ -152,6 +209,8 @@ public boolean isPeeled() {
 
 	private final ObjectId objectId;
 
+	private final long updateIndex;
+
 	/**
 	 * Create a new ref pairing.
 	 *
@@ -162,12 +221,16 @@ public boolean isPeeled() {
 	 * @param id
 	 *            current value of the ref. May be {@code null} to indicate a
 	 *            ref that does not exist yet.
+	 * @param updateIndex
+	 *            number that increases with each ref update. Set to -1 if the
+	 *            storage doesn't support versioning.
 	 */
 	protected ObjectIdRef(@NonNull Storage st, @NonNull String name,
-			@Nullable ObjectId id) {
+			@Nullable ObjectId id, long updateIndex) {
 		this.name = name;
 		this.storage = st;
 		this.objectId = id;
+		this.updateIndex = updateIndex;
 	}
 
 	/** {@inheritDoc} */
@@ -211,6 +274,15 @@ public Storage getStorage() {
 		return storage;
 	}
 
+	/** {@inheritDoc} */
+	@Override
+	public long getUpdateIndex() {
+		if (updateIndex == -1) {
+			throw new UnsupportedOperationException();
+		}
+		return updateIndex;
+	}
+
 	/** {@inheritDoc} */
 	@NonNull
 	@Override
@@ -220,7 +292,9 @@ public String toString() {
 		r.append(getName());
 		r.append('=');
 		r.append(ObjectId.toString(getObjectId()));
-		r.append(']');
+		r.append('(');
+		r.append(updateIndex); // Print value, even if -1
+		r.append(")]"); //$NON-NLS-1$
 		return r.toString();
 	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/lib/Ref.java

@@ -217,4 +217,27 @@ public boolean isPacked() {
 	 */
 	@NonNull
 	Storage getStorage();
+
+	/**
+	 * Indicator of the relative order between updates of a specific reference
+	 * name. A number that increases when a reference is updated.
+	 * <p>
+	 * With symbolic references, the update index refers to updates of the
+	 * symbolic reference itself. For example, if HEAD points to
+	 * refs/heads/master, then the update index for exactRef("HEAD") will only
+	 * increase when HEAD changes to point to another ref, regardless of how
+	 * many times refs/heads/master is updated.
+	 * <p>
+	 * Should not be used unless the {@code RefDatabase} that instantiated the
+	 * ref supports versioning (see {@link RefDatabase#hasVersioning()})
+	 *
+	 * @return the update index (i.e. version) of this reference.
+	 * @throws UnsupportedOperationException
+	 *             if the creator of the instance (e.g. {@link RefDatabase})
+	 *             doesn't support versioning and doesn't override this method
+	 * @since 5.3
+	 */
+	default long getUpdateIndex() {
+		throw new UnsupportedOperationException();
+	}
 }

org.eclipse.jgit/src/org/eclipse/jgit/lib/RefDatabase.java

@@ -110,6 +110,19 @@ public abstract class RefDatabase {
 	 */
 	public abstract void close();
 
+	/**
+	 * With versioning, each reference has a version number that increases on
+	 * update. See {@link Ref#getUpdateIndex()}.
+	 *
+	 * @implSpec This method returns false by default. Implementations
+	 *           supporting versioning must override it to return true.
+	 * @return true if the implementation assigns update indices to references.
+	 * @since 5.3
+	 */
+	public boolean hasVersioning() {
+		return false;
+	}
+
 	/**
 	 * Determine if a proposed reference name overlaps with an existing one.
 	 * <p>

org.eclipse.jgit/src/org/eclipse/jgit/lib/SymbolicRef.java

@@ -58,6 +58,8 @@ public class SymbolicRef implements Ref {
 
 	private final Ref target;
 
+	private final long updateIndex;
+
 	/**
 	 * Create a new ref pairing.
 	 *
@@ -69,6 +71,24 @@ public class SymbolicRef implements Ref {
 	public SymbolicRef(@NonNull String refName, @NonNull Ref target) {
 		this.name = refName;
 		this.target = target;
+		this.updateIndex = -1;
+	}
+
+	/**
+	 * Create a new ref pairing.
+	 *
+	 * @param refName
+	 *            name of this ref.
+	 * @param target
+	 *            the ref we reference and derive our value from.
+	 * @param updateIndex
+	 *            index that increases with each update of the reference
+	 */
+	public SymbolicRef(@NonNull String refName, @NonNull Ref target,
+			long updateIndex) {
+		this.name = refName;
+		this.target = target;
+		this.updateIndex = updateIndex;
 	}
 
 	/** {@inheritDoc} */
@@ -128,6 +148,15 @@ public boolean isPeeled() {
 		return getLeaf().isPeeled();
 	}
 
+	/** {@inheritDoc} */
+	@Override
+	public long getUpdateIndex() {
+		if (updateIndex == -1) {
+			throw new UnsupportedOperationException();
+		}
+		return updateIndex;
+	}
+
 	/** {@inheritDoc} */
 	@SuppressWarnings("nls")
 	@Override
@@ -143,7 +172,9 @@ public String toString() {
 		r.append(cur.getName());
 		r.append('=');
 		r.append(ObjectId.toString(cur.getObjectId()));
-		r.append("]");
+		r.append("(");
+		r.append(updateIndex); // Print value, even if -1
+		r.append(")]");
 		return r.toString();
 	}
 }