diff --git a/.bazelversion b/.bazelversion
index 3eefcb9dd..227cea215 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-1.0.0
+2.0.0
diff --git a/WORKSPACE b/WORKSPACE
index dc89a6c54..8e6b8642b 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -15,7 +15,7 @@ versions.check(minimum_bazel_version = "0.29.0")
 
 load("//tools:bazlets.bzl", "load_bazlets")
 
-load_bazlets(commit = "09a035e98077dce549d5f6a7472d06c4b8f792d2")
+load_bazlets(commit = "f53f51fb660552d0581aa0ba52c3836ed63d56a3")
 
 load(
     "@com_googlesource_gerrit_bazlets//tools:maven_jar.bzl",
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/BatchRefUpdateTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/BatchRefUpdateTest.java
index 2ac4a846e..d0e3943d1 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/BatchRefUpdateTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/file/BatchRefUpdateTest.java
@@ -205,16 +205,32 @@ public void simpleNoForce() throws IOException {
 			assertRefs(
 					"refs/heads/master", A,
 					"refs/heads/masters", B);
-			assertEquals(1, refsChangedEvents);
 		} else {
 			assertResults(cmds, OK, REJECTED_NONFASTFORWARD);
 			assertRefs(
 					"refs/heads/master", B,
 					"refs/heads/masters", B);
-			assertEquals(2, refsChangedEvents);
 		}
 	}
 
+	@Test
+	public void simpleNoForceRefsChangedEvents() throws IOException {
+		writeLooseRef("refs/heads/master", A);
+		writeLooseRef("refs/heads/masters", B);
+		refdir.exactRef("refs/heads/master");
+		refdir.exactRef("refs/heads/masters");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		List<ReceiveCommand> cmds = Arrays.asList(
+				new ReceiveCommand(A, B, "refs/heads/master", UPDATE),
+				new ReceiveCommand(B, A, "refs/heads/masters",
+						UPDATE_NONFASTFORWARD));
+		execute(newBatchUpdate(cmds));
+
+		assertEquals(atomic ? initialRefsChangedEvents
+				: initialRefsChangedEvents + 1, refsChangedEvents);
+	}
+
 	@Test
 	public void simpleForce() throws IOException {
 		writeLooseRef("refs/heads/master", A);
@@ -229,7 +245,24 @@ public void simpleForce() throws IOException {
 		assertRefs(
 				"refs/heads/master", B,
 				"refs/heads/masters", A);
-		assertEquals(atomic ? 2 : 3, refsChangedEvents);
+	}
+
+	@Test
+	public void simpleForceRefsChangedEvents() throws IOException {
+		writeLooseRef("refs/heads/master", A);
+		writeLooseRef("refs/heads/masters", B);
+		refdir.exactRef("refs/heads/master");
+		refdir.exactRef("refs/heads/masters");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		List<ReceiveCommand> cmds = Arrays.asList(
+				new ReceiveCommand(A, B, "refs/heads/master", UPDATE),
+				new ReceiveCommand(B, A, "refs/heads/masters",
+						UPDATE_NONFASTFORWARD));
+		execute(newBatchUpdate(cmds).setAllowNonFastForwards(true));
+
+		assertEquals(atomic ? initialRefsChangedEvents + 1
+				: initialRefsChangedEvents + 2, refsChangedEvents);
 	}
 
 	@Test
@@ -251,7 +284,28 @@ public boolean isMergedInto(RevCommit base, RevCommit tip) {
 
 		assertResults(cmds, OK);
 		assertRefs("refs/heads/master", A);
-		assertEquals(2, refsChangedEvents);
+	}
+
+	@Test
+	public void nonFastForwardDoesNotDoExpensiveMergeCheckRefsChangedEvents()
+			throws IOException {
+		writeLooseRef("refs/heads/master", B);
+		refdir.exactRef("refs/heads/master");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		List<ReceiveCommand> cmds = Arrays.asList(new ReceiveCommand(B, A,
+				"refs/heads/master", UPDATE_NONFASTFORWARD));
+		try (RevWalk rw = new RevWalk(diskRepo) {
+			@Override
+			public boolean isMergedInto(RevCommit base, RevCommit tip) {
+				throw new AssertionError("isMergedInto() should not be called");
+			}
+		}) {
+			newBatchUpdate(cmds).setAllowNonFastForwards(true).execute(rw,
+					new StrictWorkMonitor());
+		}
+
+		assertEquals(initialRefsChangedEvents + 1, refsChangedEvents);
 	}
 
 	@Test
@@ -273,7 +327,6 @@ public void fileDirectoryConflict() throws IOException {
 			assertRefs(
 					"refs/heads/master", A,
 					"refs/heads/masters", B);
-			assertEquals(1, refsChangedEvents);
 		} else {
 			// Non-atomic updates are applied in order: master succeeds, then master/x
 			// fails due to conflict.
@@ -281,10 +334,27 @@ public void fileDirectoryConflict() throws IOException {
 			assertRefs(
 					"refs/heads/master", B,
 					"refs/heads/masters", B);
-			assertEquals(2, refsChangedEvents);
 		}
 	}
 
+	@Test
+	public void fileDirectoryConflictRefsChangedEvents() throws IOException {
+		writeLooseRef("refs/heads/master", A);
+		writeLooseRef("refs/heads/masters", B);
+		refdir.exactRef("refs/heads/master");
+		refdir.exactRef("refs/heads/masters");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		List<ReceiveCommand> cmds = Arrays.asList(
+				new ReceiveCommand(A, B, "refs/heads/master", UPDATE),
+				new ReceiveCommand(zeroId(), A, "refs/heads/master/x", CREATE),
+				new ReceiveCommand(zeroId(), A, "refs/heads", CREATE));
+		execute(newBatchUpdate(cmds).setAllowNonFastForwards(true), false);
+
+		assertEquals(atomic ? initialRefsChangedEvents
+				: initialRefsChangedEvents + 1, refsChangedEvents);
+	}
+
 	@Test
 	public void conflictThanksToDelete() throws IOException {
 		writeLooseRef("refs/heads/master", A);
@@ -300,15 +370,24 @@ public void conflictThanksToDelete() throws IOException {
 		assertRefs(
 				"refs/heads/master", B,
 				"refs/heads/masters/x", A);
-		if (atomic) {
-			assertEquals(2, refsChangedEvents);
-		} else {
-			// The non-atomic case actually produces 5 events, but that's an
-			// implementation detail. We expect at least 4 events, one for the
-			// initial read due to writeLooseRef(), and then one for each
-			// successful ref update.
-			assertTrue(refsChangedEvents >= 4);
-		}
+	}
+
+	@Test
+	public void conflictThanksToDeleteRefsChangedEvents() throws IOException {
+		writeLooseRef("refs/heads/master", A);
+		writeLooseRef("refs/heads/masters", B);
+		refdir.exactRef("refs/heads/master");
+		refdir.exactRef("refs/heads/masters");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		List<ReceiveCommand> cmds = Arrays.asList(
+				new ReceiveCommand(A, B, "refs/heads/master", UPDATE),
+				new ReceiveCommand(zeroId(), A, "refs/heads/masters/x", CREATE),
+				new ReceiveCommand(B, zeroId(), "refs/heads/masters", DELETE));
+		execute(newBatchUpdate(cmds).setAllowNonFastForwards(true));
+
+		assertEquals(atomic ? initialRefsChangedEvents + 1
+				: initialRefsChangedEvents + 3, refsChangedEvents);
 	}
 
 	@Test
@@ -325,16 +404,31 @@ public void updateToMissingObject() throws IOException {
 		if (atomic) {
 			assertResults(cmds, REJECTED_MISSING_OBJECT, TRANSACTION_ABORTED);
 			assertRefs("refs/heads/master", A);
-			assertEquals(1, refsChangedEvents);
 		} else {
 			assertResults(cmds, REJECTED_MISSING_OBJECT, OK);
 			assertRefs(
 					"refs/heads/master", A,
 					"refs/heads/foo2", B);
-			assertEquals(2, refsChangedEvents);
 		}
 	}
 
+	@Test
+	public void updateToMissingObjectRefsChangedEvents() throws IOException {
+		writeLooseRef("refs/heads/master", A);
+		refdir.exactRef("refs/heads/master");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		ObjectId bad = ObjectId
+				.fromString("deadbeefdeadbeefdeadbeefdeadbeefdeadbeef");
+		List<ReceiveCommand> cmds = Arrays.asList(
+				new ReceiveCommand(A, bad, "refs/heads/master", UPDATE),
+				new ReceiveCommand(zeroId(), B, "refs/heads/foo2", CREATE));
+		execute(newBatchUpdate(cmds).setAllowNonFastForwards(true), false);
+
+		assertEquals(atomic ? initialRefsChangedEvents
+				: initialRefsChangedEvents + 1, refsChangedEvents);
+	}
+
 	@Test
 	public void addMissingObject() throws IOException {
 		writeLooseRef("refs/heads/master", A);
@@ -349,14 +443,29 @@ public void addMissingObject() throws IOException {
 		if (atomic) {
 			assertResults(cmds, TRANSACTION_ABORTED, REJECTED_MISSING_OBJECT);
 			assertRefs("refs/heads/master", A);
-			assertEquals(1, refsChangedEvents);
 		} else {
 			assertResults(cmds, OK, REJECTED_MISSING_OBJECT);
 			assertRefs("refs/heads/master", B);
-			assertEquals(2, refsChangedEvents);
 		}
 	}
 
+	@Test
+	public void addMissingObjectRefsChangedEvents() throws IOException {
+		writeLooseRef("refs/heads/master", A);
+		refdir.exactRef("refs/heads/master");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		ObjectId bad = ObjectId
+				.fromString("deadbeefdeadbeefdeadbeefdeadbeefdeadbeef");
+		List<ReceiveCommand> cmds = Arrays.asList(
+				new ReceiveCommand(A, B, "refs/heads/master", UPDATE),
+				new ReceiveCommand(zeroId(), bad, "refs/heads/foo2", CREATE));
+		execute(newBatchUpdate(cmds).setAllowNonFastForwards(true), false);
+
+		assertEquals(atomic ? initialRefsChangedEvents
+				: initialRefsChangedEvents + 1, refsChangedEvents);
+	}
+
 	@Test
 	public void oneNonExistentRef() throws IOException {
 		List<ReceiveCommand> cmds = Arrays.asList(
@@ -387,16 +496,29 @@ public void oneRefWrongOldValue() throws IOException {
 		if (atomic) {
 			assertResults(cmds, LOCK_FAILURE, TRANSACTION_ABORTED);
 			assertRefs("refs/heads/master", A);
-			assertEquals(1, refsChangedEvents);
 		} else {
 			assertResults(cmds, LOCK_FAILURE, OK);
 			assertRefs(
 					"refs/heads/master", A,
 					"refs/heads/foo2", B);
-			assertEquals(2, refsChangedEvents);
 		}
 	}
 
+	@Test
+	public void oneRefWrongOldValueRefsChangedEvents() throws IOException {
+		writeLooseRef("refs/heads/master", A);
+		refdir.exactRef("refs/heads/master");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		List<ReceiveCommand> cmds = Arrays.asList(
+				new ReceiveCommand(B, B, "refs/heads/master", UPDATE),
+				new ReceiveCommand(zeroId(), B, "refs/heads/foo2", CREATE));
+		execute(newBatchUpdate(cmds).setAllowNonFastForwards(true));
+
+		assertEquals(atomic ? initialRefsChangedEvents
+				: initialRefsChangedEvents + 1, refsChangedEvents);
+	}
+
 	@Test
 	public void nonExistentRef() throws IOException {
 		writeLooseRef("refs/heads/master", A);
@@ -409,17 +531,31 @@ public void nonExistentRef() throws IOException {
 		if (atomic) {
 			assertResults(cmds, TRANSACTION_ABORTED, LOCK_FAILURE);
 			assertRefs("refs/heads/master", A);
-			assertEquals(1, refsChangedEvents);
 		} else {
 			assertResults(cmds, OK, LOCK_FAILURE);
 			assertRefs("refs/heads/master", B);
-			assertEquals(2, refsChangedEvents);
 		}
 	}
 
+	@Test
+	public void nonExistentRefRefsChangedEvents() throws IOException {
+		writeLooseRef("refs/heads/master", A);
+		refdir.exactRef("refs/heads/master");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		List<ReceiveCommand> cmds = Arrays.asList(
+				new ReceiveCommand(A, B, "refs/heads/master", UPDATE),
+				new ReceiveCommand(A, zeroId(), "refs/heads/foo2", DELETE));
+		execute(newBatchUpdate(cmds).setAllowNonFastForwards(true));
+
+		assertEquals(atomic ? initialRefsChangedEvents
+				: initialRefsChangedEvents + 1, refsChangedEvents);
+	}
+
 	@Test
 	public void noRefLog() throws IOException {
 		writeRef("refs/heads/master", A);
+		int initialRefsChangedEvents = refsChangedEvents;
 
 		Map<String, ReflogEntry> oldLogs =
 				getLastReflogs("refs/heads/master", "refs/heads/branch");
@@ -434,7 +570,8 @@ public void noRefLog() throws IOException {
 		assertRefs(
 				"refs/heads/master", B,
 				"refs/heads/branch", B);
-		assertEquals(atomic ? 2 : 3, refsChangedEvents);
+		assertEquals(atomic ? initialRefsChangedEvents + 1
+				: initialRefsChangedEvents + 2, refsChangedEvents);
 		assertReflogUnchanged(oldLogs, "refs/heads/master");
 		assertReflogUnchanged(oldLogs, "refs/heads/branch");
 	}
@@ -443,6 +580,7 @@ public void noRefLog() throws IOException {
 	public void reflogDefaultIdent() throws IOException {
 		writeRef("refs/heads/master", A);
 		writeRef("refs/heads/branch2", A);
+		int initialRefsChangedEvents = refsChangedEvents;
 
 		Map<String, ReflogEntry> oldLogs = getLastReflogs(
 				"refs/heads/master", "refs/heads/branch1", "refs/heads/branch2");
@@ -459,7 +597,8 @@ public void reflogDefaultIdent() throws IOException {
 				"refs/heads/master", B,
 				"refs/heads/branch1", B,
 				"refs/heads/branch2", A);
-		assertEquals(atomic ? 3 : 4, refsChangedEvents);
+		assertEquals(atomic ? initialRefsChangedEvents + 1
+				: initialRefsChangedEvents + 2, refsChangedEvents);
 		assertReflogEquals(
 				reflog(A, B, new PersonIdent(diskRepo), "a reflog"),
 				getLastReflog("refs/heads/master"));
@@ -473,6 +612,7 @@ public void reflogDefaultIdent() throws IOException {
 	public void reflogAppendStatusNoMessage() throws IOException {
 		writeRef("refs/heads/master", A);
 		writeRef("refs/heads/branch1", B);
+		int initialRefsChangedEvents = refsChangedEvents;
 
 		List<ReceiveCommand> cmds = Arrays.asList(
 				new ReceiveCommand(A, B, "refs/heads/master", UPDATE),
@@ -488,7 +628,9 @@ public void reflogAppendStatusNoMessage() throws IOException {
 				"refs/heads/master", B,
 				"refs/heads/branch1", A,
 				"refs/heads/branch2", A);
-		assertEquals(atomic ? 3 : 5, refsChangedEvents);
+		assertEquals(atomic ? initialRefsChangedEvents + 1
+				: initialRefsChangedEvents + 3,
+				refsChangedEvents);
 		assertReflogEquals(
 				// Always forced; setAllowNonFastForwards(true) bypasses the check.
 				reflog(A, B, new PersonIdent(diskRepo), "forced-update"),
@@ -504,6 +646,7 @@ public void reflogAppendStatusNoMessage() throws IOException {
 	@Test
 	public void reflogAppendStatusFastForward() throws IOException {
 		writeRef("refs/heads/master", A);
+		int initialRefsChangedEvents = refsChangedEvents;
 
 		List<ReceiveCommand> cmds = Arrays.asList(
 				new ReceiveCommand(A, B, "refs/heads/master", UPDATE));
@@ -511,7 +654,7 @@ public void reflogAppendStatusFastForward() throws IOException {
 
 		assertResults(cmds, OK);
 		assertRefs("refs/heads/master", B);
-		assertEquals(2, refsChangedEvents);
+		assertEquals(initialRefsChangedEvents + 1, refsChangedEvents);
 		assertReflogEquals(
 				reflog(A, B, new PersonIdent(diskRepo), "fast-forward"),
 				getLastReflog("refs/heads/master"));
@@ -520,6 +663,7 @@ public void reflogAppendStatusFastForward() throws IOException {
 	@Test
 	public void reflogAppendStatusWithMessage() throws IOException {
 		writeRef("refs/heads/master", A);
+		int initialRefsChangedEvents = refsChangedEvents;
 
 		List<ReceiveCommand> cmds = Arrays.asList(
 				new ReceiveCommand(A, B, "refs/heads/master", UPDATE),
@@ -530,7 +674,8 @@ public void reflogAppendStatusWithMessage() throws IOException {
 		assertRefs(
 				"refs/heads/master", B,
 				"refs/heads/branch", A);
-		assertEquals(atomic ? 2 : 3, refsChangedEvents);
+		assertEquals(atomic ? initialRefsChangedEvents + 1
+				: initialRefsChangedEvents + 2, refsChangedEvents);
 		assertReflogEquals(
 				reflog(A, B, new PersonIdent(diskRepo), "a reflog: fast-forward"),
 				getLastReflog("refs/heads/master"));
@@ -542,6 +687,7 @@ public void reflogAppendStatusWithMessage() throws IOException {
 	@Test
 	public void reflogCustomIdent() throws IOException {
 		writeRef("refs/heads/master", A);
+		int initialRefsChangedEvents = refsChangedEvents;
 
 		List<ReceiveCommand> cmds = Arrays.asList(
 				new ReceiveCommand(A, B, "refs/heads/master", UPDATE),
@@ -553,7 +699,8 @@ public void reflogCustomIdent() throws IOException {
 						.setRefLogIdent(ident));
 
 		assertResults(cmds, OK, OK);
-		assertEquals(atomic ? 2 : 3, refsChangedEvents);
+		assertEquals(atomic ? initialRefsChangedEvents + 1
+				: initialRefsChangedEvents + 2, refsChangedEvents);
 		assertRefs(
 				"refs/heads/master", B,
 				"refs/heads/branch", B);
@@ -571,6 +718,8 @@ public void reflogCustomIdent() throws IOException {
 	public void reflogDelete() throws IOException {
 		writeRef("refs/heads/master", A);
 		writeRef("refs/heads/branch", A);
+		int initialRefsChangedEvents = refsChangedEvents;
+
 		assertEquals(
 				2, getLastReflogs("refs/heads/master", "refs/heads/branch").size());
 
@@ -581,7 +730,8 @@ public void reflogDelete() throws IOException {
 
 		assertResults(cmds, OK, OK);
 		assertRefs("refs/heads/branch", B);
-		assertEquals(atomic ? 3 : 4, refsChangedEvents);
+		assertEquals(atomic ? initialRefsChangedEvents + 1
+				: initialRefsChangedEvents + 2, refsChangedEvents);
 		assertNull(getLastReflog("refs/heads/master"));
 		assertReflogEquals(
 				reflog(A, B, new PersonIdent(diskRepo), "a reflog"),
@@ -591,6 +741,7 @@ public void reflogDelete() throws IOException {
 	@Test
 	public void reflogFileDirectoryConflict() throws IOException {
 		writeRef("refs/heads/master", A);
+		int initialRefsChangedEvents = refsChangedEvents;
 
 		List<ReceiveCommand> cmds = Arrays.asList(
 				new ReceiveCommand(A, zeroId(), "refs/heads/master", DELETE),
@@ -599,7 +750,8 @@ public void reflogFileDirectoryConflict() throws IOException {
 
 		assertResults(cmds, OK, OK);
 		assertRefs("refs/heads/master/x", A);
-		assertEquals(atomic ? 2 : 3, refsChangedEvents);
+		assertEquals(atomic ? initialRefsChangedEvents + 1
+				: initialRefsChangedEvents + 2, refsChangedEvents);
 		assertNull(getLastReflog("refs/heads/master"));
 		assertReflogEquals(
 				reflog(zeroId(), A, new PersonIdent(diskRepo), "a reflog"),
@@ -609,6 +761,7 @@ public void reflogFileDirectoryConflict() throws IOException {
 	@Test
 	public void reflogOnLockFailure() throws IOException {
 		writeRef("refs/heads/master", A);
+		int initialRefsChangedEvents = refsChangedEvents;
 
 		Map<String, ReflogEntry> oldLogs =
 				getLastReflogs("refs/heads/master", "refs/heads/branch");
@@ -620,12 +773,12 @@ public void reflogOnLockFailure() throws IOException {
 
 		if (atomic) {
 			assertResults(cmds, TRANSACTION_ABORTED, LOCK_FAILURE);
-			assertEquals(1, refsChangedEvents);
+			assertEquals(initialRefsChangedEvents, refsChangedEvents);
 			assertReflogUnchanged(oldLogs, "refs/heads/master");
 			assertReflogUnchanged(oldLogs, "refs/heads/branch");
 		} else {
 			assertResults(cmds, OK, LOCK_FAILURE);
-			assertEquals(2, refsChangedEvents);
+			assertEquals(initialRefsChangedEvents + 1, refsChangedEvents);
 			assertReflogEquals(
 					reflog(A, B, new PersonIdent(diskRepo), "a reflog"),
 					getLastReflog("refs/heads/master"));
@@ -636,6 +789,7 @@ public void reflogOnLockFailure() throws IOException {
 	@Test
 	public void overrideRefLogMessage() throws Exception {
 		writeRef("refs/heads/master", A);
+		int initialRefsChangedEvents = refsChangedEvents;
 
 		List<ReceiveCommand> cmds = Arrays.asList(
 				new ReceiveCommand(A, B, "refs/heads/master", UPDATE),
@@ -648,7 +802,8 @@ public void overrideRefLogMessage() throws Exception {
 						.setRefLogMessage("a reflog", true));
 
 		assertResults(cmds, OK, OK);
-		assertEquals(atomic ? 2 : 3, refsChangedEvents);
+		assertEquals(atomic ? initialRefsChangedEvents + 1
+				: initialRefsChangedEvents + 2, refsChangedEvents);
 		assertReflogEquals(
 				reflog(A, B, ident, "custom log"),
 				getLastReflog("refs/heads/master"),
@@ -662,6 +817,7 @@ public void overrideRefLogMessage() throws Exception {
 	@Test
 	public void overrideDisableRefLog() throws Exception {
 		writeRef("refs/heads/master", A);
+		int initialRefsChangedEvents = refsChangedEvents;
 
 		Map<String, ReflogEntry> oldLogs =
 				getLastReflogs("refs/heads/master", "refs/heads/branch");
@@ -673,7 +829,8 @@ public void overrideDisableRefLog() throws Exception {
 		execute(newBatchUpdate(cmds).setRefLogMessage("a reflog", true));
 
 		assertResults(cmds, OK, OK);
-		assertEquals(atomic ? 2 : 3, refsChangedEvents);
+		assertEquals(atomic ? initialRefsChangedEvents + 1
+				: initialRefsChangedEvents + 2, refsChangedEvents);
 		assertReflogUnchanged(oldLogs, "refs/heads/master");
 		assertReflogEquals(
 				reflog(zeroId(), B, new PersonIdent(diskRepo), "a reflog: created"),
@@ -763,20 +920,41 @@ public void packedRefsLockFailure() throws Exception {
 			if (atomic) {
 				assertResults(cmds, LOCK_FAILURE, TRANSACTION_ABORTED);
 				assertRefs("refs/heads/master", A);
-				assertEquals(1, refsChangedEvents);
 			} else {
 				// Only operates on loose refs, doesn't care that packed-refs is locked.
 				assertResults(cmds, OK, OK);
 				assertRefs(
 						"refs/heads/master", B,
 						"refs/heads/branch", B);
-				assertEquals(3, refsChangedEvents);
 			}
 		} finally {
 			myLock.unlock();
 		}
 	}
 
+	@Test
+	public void packedRefsLockFailureRefsChangedEvents() throws Exception {
+		writeLooseRef("refs/heads/master", A);
+		refdir.exactRef("refs/heads/master");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		List<ReceiveCommand> cmds = Arrays.asList(
+				new ReceiveCommand(A, B, "refs/heads/master", UPDATE),
+				new ReceiveCommand(zeroId(), B, "refs/heads/branch", CREATE));
+
+		LockFile myLock = refdir.lockPackedRefs();
+		try {
+			execute(newBatchUpdate(cmds).setAllowNonFastForwards(true));
+
+			assertEquals(
+					atomic ? initialRefsChangedEvents
+							: initialRefsChangedEvents + 2,
+					refsChangedEvents);
+		} finally {
+			myLock.unlock();
+		}
+	}
+
 	@Test
 	public void oneRefLockFailure() throws Exception {
 		writeLooseRef("refs/heads/master", A);
@@ -796,19 +974,41 @@ public void oneRefLockFailure() throws Exception {
 			if (atomic) {
 				assertResults(cmds, TRANSACTION_ABORTED, LOCK_FAILURE);
 				assertRefs("refs/heads/master", A);
-				assertEquals(1, refsChangedEvents);
 			} else {
 				assertResults(cmds, OK, LOCK_FAILURE);
 				assertRefs(
 						"refs/heads/branch", B,
 						"refs/heads/master", A);
-				assertEquals(2, refsChangedEvents);
 			}
 		} finally {
 			myLock.unlock();
 		}
 	}
 
+	@Test
+	public void oneRefLockFailureRefsChangedEvents() throws Exception {
+		writeLooseRef("refs/heads/master", A);
+		refdir.exactRef("refs/heads/master");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		List<ReceiveCommand> cmds = Arrays.asList(
+				new ReceiveCommand(zeroId(), B, "refs/heads/branch", CREATE),
+				new ReceiveCommand(A, B, "refs/heads/master", UPDATE));
+
+		LockFile myLock = new LockFile(refdir.fileFor("refs/heads/master"));
+		assertTrue(myLock.lock());
+		try {
+			execute(newBatchUpdate(cmds).setAllowNonFastForwards(true));
+
+			assertEquals(
+					atomic ? initialRefsChangedEvents
+							: initialRefsChangedEvents + 1,
+					refsChangedEvents);
+		} finally {
+			myLock.unlock();
+		}
+	}
+
 	@Test
 	public void singleRefUpdateDoesNotRequirePackedRefsLock() throws Exception {
 		writeLooseRef("refs/heads/master", A);
@@ -822,13 +1022,32 @@ public void singleRefUpdateDoesNotRequirePackedRefsLock() throws Exception {
 
 			assertFalse(getLockFile("refs/heads/master").exists());
 			assertResults(cmds, OK);
-			assertEquals(2, refsChangedEvents);
 			assertRefs("refs/heads/master", B);
 		} finally {
 			myLock.unlock();
 		}
 	}
 
+	@Test
+	public void singleRefUpdateDoesNotRequirePackedRefsLockRefsChangedEvents()
+			throws Exception {
+		writeLooseRef("refs/heads/master", A);
+		refdir.exactRef("refs/heads/master");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		List<ReceiveCommand> cmds = Arrays
+				.asList(new ReceiveCommand(A, B, "refs/heads/master", UPDATE));
+
+		LockFile myLock = refdir.lockPackedRefs();
+		try {
+			execute(newBatchUpdate(cmds).setAllowNonFastForwards(true));
+
+			assertEquals(initialRefsChangedEvents + 1, refsChangedEvents);
+		} finally {
+			myLock.unlock();
+		}
+	}
+
 	@Test
 	public void atomicUpdateRespectsInProcessLock() throws Exception {
 		assumeTrue(atomic);
@@ -881,6 +1100,53 @@ public void atomicUpdateRespectsInProcessLock() throws Exception {
 				"refs/heads/branch", B);
 	}
 
+	@Test
+	public void atomicUpdateRespectsInProcessLockRefsChangedEvents()
+			throws Exception {
+		assumeTrue(atomic);
+
+		writeLooseRef("refs/heads/master", A);
+		refdir.exactRef("refs/heads/master");
+		int initialRefsChangedEvents = refsChangedEvents;
+
+		List<ReceiveCommand> cmds = Arrays.asList(
+				new ReceiveCommand(A, B, "refs/heads/master", UPDATE),
+				new ReceiveCommand(zeroId(), B, "refs/heads/branch", CREATE));
+
+		Thread t = new Thread(() -> {
+			try {
+				execute(newBatchUpdate(cmds).setAllowNonFastForwards(true));
+			} catch (Exception e) {
+				throw new RuntimeException(e);
+			}
+		});
+
+		ReentrantLock l = refdir.inProcessPackedRefsLock;
+		l.lock();
+		try {
+			t.start();
+			long timeoutSecs = 10;
+
+			// Hold onto the lock until we observe the worker thread has
+			// attempted to
+			// acquire it.
+			while (l.getQueueLength() == 0) {
+				Thread.sleep(3);
+			}
+
+			// Once we unlock, the worker thread should finish the update
+			// promptly.
+			l.unlock();
+			t.join(SECONDS.toMillis(timeoutSecs));
+		} finally {
+			if (l.isHeldByCurrentThread()) {
+				l.unlock();
+			}
+		}
+
+		assertEquals(initialRefsChangedEvents + 1, refsChangedEvents);
+	}
+
 	private void setLogAllRefUpdates(boolean enable) throws Exception {
 		StoredConfig cfg = diskRepo.getConfig();
 		cfg.load();
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
index a4729bba4..6153ac5e1 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/RefDirectory.java
@@ -277,47 +277,18 @@ public void refresh() {
 	/** {@inheritDoc} */
 	@Override
 	public boolean isNameConflicting(String name) throws IOException {
-		RefList<Ref> packed = getPackedRefs();
-		RefList<LooseRef> loose = getLooseRefs();
-
 		// Cannot be nested within an existing reference.
 		int lastSlash = name.lastIndexOf('/');
 		while (0 < lastSlash) {
 			String needle = name.substring(0, lastSlash);
-			if (loose.contains(needle) || packed.contains(needle))
+			if (exactRef(needle) != null) {
 				return true;
+			}
 			lastSlash = name.lastIndexOf('/', lastSlash - 1);
 		}
 
 		// Cannot be the container of an existing reference.
-		String prefix = name + '/';
-		int idx;
-
-		idx = -(packed.find(prefix) + 1);
-		if (idx < packed.size() && packed.get(idx).getName().startsWith(prefix))
-			return true;
-
-		idx = -(loose.find(prefix) + 1);
-		if (idx < loose.size() && loose.get(idx).getName().startsWith(prefix))
-			return true;
-
-		return false;
-	}
-
-	private RefList<LooseRef> getLooseRefs() {
-		final RefList<LooseRef> oldLoose = looseRefs.get();
-
-		LooseScanner scan = new LooseScanner(oldLoose);
-		scan.scan(ALL);
-
-		RefList<LooseRef> loose;
-		if (scan.newLoose != null) {
-			loose = scan.newLoose.toRefList();
-			if (looseRefs.compareAndSet(oldLoose, loose))
-				modCnt.incrementAndGet();
-		} else
-			loose = oldLoose;
-		return loose;
+		return !getRefsByPrefix(name + '/').isEmpty();
 	}
 
 	@Nullable
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/BatchRefUpdate.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/BatchRefUpdate.java
index 925b6bead..46d2ab339 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/BatchRefUpdate.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/BatchRefUpdate.java
@@ -46,7 +46,6 @@
 
 import static org.eclipse.jgit.transport.ReceiveCommand.Result.NOT_ATTEMPTED;
 import static org.eclipse.jgit.transport.ReceiveCommand.Result.REJECTED_OTHER_REASON;
-import static java.util.stream.Collectors.toCollection;
 
 import java.io.IOException;
 import java.text.MessageFormat;
@@ -62,7 +61,6 @@
 import org.eclipse.jgit.annotations.Nullable;
 import org.eclipse.jgit.errors.MissingObjectException;
 import org.eclipse.jgit.internal.JGitText;
-import org.eclipse.jgit.lib.RefUpdate.Result;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.transport.PushCertificate;
 import org.eclipse.jgit.transport.ReceiveCommand;
@@ -528,42 +526,24 @@ public void execute(RevWalk walk, ProgressMonitor monitor,
 			}
 		}
 		if (!commands2.isEmpty()) {
-			// What part of the name space is already taken
-			Collection<String> takenNames = refdb.getRefs().stream()
-					.map(Ref::getName)
-					.collect(toCollection(HashSet::new));
-			Collection<String> takenPrefixes = getTakenPrefixes(takenNames);
-
-			// Now to the update that may require more room in the name space
+			// Perform updates that may require more room in the name space
 			for (ReceiveCommand cmd : commands2) {
 				try {
 					if (cmd.getResult() == NOT_ATTEMPTED) {
 						cmd.updateType(walk);
 						RefUpdate ru = newUpdate(cmd);
-						SWITCH: switch (cmd.getType()) {
-						case DELETE:
-							// Performed in the first phase
-							break;
-						case UPDATE:
-						case UPDATE_NONFASTFORWARD:
-							RefUpdate ruu = newUpdate(cmd);
-							cmd.setResult(ruu.update(walk));
-							break;
-						case CREATE:
-							for (String prefix : getPrefixes(cmd.getRefName())) {
-								if (takenNames.contains(prefix)) {
-									cmd.setResult(Result.LOCK_FAILURE);
-									break SWITCH;
-								}
-							}
-							if (takenPrefixes.contains(cmd.getRefName())) {
-								cmd.setResult(Result.LOCK_FAILURE);
-								break SWITCH;
-							}
-							ru.setCheckConflicting(false);
-							takenPrefixes.addAll(getPrefixes(cmd.getRefName()));
-							takenNames.add(cmd.getRefName());
-							cmd.setResult(ru.update(walk));
+						switch (cmd.getType()) {
+							case DELETE:
+								// Performed in the first phase
+								break;
+							case UPDATE:
+							case UPDATE_NONFASTFORWARD:
+								RefUpdate ruu = newUpdate(cmd);
+								cmd.setResult(ruu.update(walk));
+								break;
+							case CREATE:
+								cmd.setResult(ru.update(walk));
+								break;
 						}
 					}
 				} catch (IOException err) {
@@ -635,14 +615,6 @@ public void execute(RevWalk walk, ProgressMonitor monitor)
 		execute(walk, monitor, null);
 	}
 
-	private static Collection<String> getTakenPrefixes(Collection<String> names) {
-		Collection<String> ref = new HashSet<>();
-		for (String name : names) {
-			addPrefixesTo(name, ref);
-		}
-		return ref;
-	}
-
 	/**
 	 * Get all path prefixes of a ref name.
 	 *