reftable: enforce ordering for ref and log writes

Previously, the API did not enforce ordering of writes.  Misuse of
this API would lead to data effectively being lost.

Guard against that with IllegalArgumentException, and add a test.

Change-Id: I04f55c481d60532fc64d35fa32c47037a03988ae
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>

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

@@ -46,13 +46,16 @@ package org.eclipse.jgit.internal.storage.reftable;
 import static org.eclipse.jgit.lib.Constants.HEAD;
 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.MoreAsserts.assertThrows;
 import static org.eclipse.jgit.lib.Ref.Storage.NEW;
 import static org.eclipse.jgit.lib.Ref.Storage.PACKED;
+import static org.hamcrest.CoreMatchers.containsString;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
@@ -414,6 +417,54 @@ public class ReftableTest {
 		assertSeek(refs, read(table));
 	}
 
+	@Test
+	public void invalidRefWriteOrder() throws IOException {
+		Ref master = ref(MASTER, 1);
+		Ref next = ref(NEXT, 2);
+		ReftableWriter writer = new ReftableWriter()
+			.setMinUpdateIndex(1)
+			.setMaxUpdateIndex(1)
+			.begin(new ByteArrayOutputStream());
+
+		writer.writeRef(next);
+		IllegalArgumentException e  = assertThrows(
+			IllegalArgumentException.class,
+			() -> writer.writeRef(master));
+		assertThat(e.getMessage(), containsString("records must be increasing"));
+	}
+
+	@Test
+	public void invalidReflogWriteOrderUpdateIndex() throws IOException {
+		ReftableWriter writer = new ReftableWriter()
+			.setMinUpdateIndex(1)
+			.setMaxUpdateIndex(2)
+			.begin(new ByteArrayOutputStream());
+		PersonIdent who = new PersonIdent("Log", "Ger", 1500079709, -8 * 60);
+		String msg = "test";
+
+		writer.writeLog(MASTER, 1, who, ObjectId.zeroId(), id(1), msg);
+		IllegalArgumentException e  = assertThrows(IllegalArgumentException.class,
+			() -> writer.writeLog(
+				MASTER, 2, who, ObjectId.zeroId(), id(2), msg));
+		assertThat(e.getMessage(), containsString("records must be increasing"));
+	}
+
+	@Test
+	public void invalidReflogWriteOrderName() throws IOException {
+		ReftableWriter writer = new ReftableWriter()
+			.setMinUpdateIndex(1)
+			.setMaxUpdateIndex(1)
+			.begin(new ByteArrayOutputStream());
+		PersonIdent who = new PersonIdent("Log", "Ger", 1500079709, -8 * 60);
+		String msg = "test";
+
+		writer.writeLog(NEXT, 1, who, ObjectId.zeroId(), id(1), msg);
+		IllegalArgumentException e = assertThrows(IllegalArgumentException.class,
+			() -> writer.writeLog(
+				MASTER, 1, who, ObjectId.zeroId(), id(2), msg));
+		assertThat(e.getMessage(), containsString("records must be increasing"));
+	}
+
 	@Test
 	public void withReflog() throws IOException {
 		Ref master = ref(MASTER, 1);
@@ -577,7 +628,7 @@ public class ReftableTest {
 
 		List<Ref> refs = new ArrayList<>();
 		for (int i = 1; i <= 5670; i++) {
-			Ref ref = ref(String.format("refs/heads/%03d", i), i);
+			Ref ref = ref(String.format("refs/heads/%04d", i), i);
 			refs.add(ref);
 			writer.writeRef(ref);
 		}

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

@@ -44,6 +44,7 @@
 package org.eclipse.jgit.internal.storage.reftable;
 
 import static java.lang.Math.log;
+import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.eclipse.jgit.internal.storage.reftable.BlockWriter.padBetweenBlocks;
 import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.FILE_FOOTER_LEN;
 import static org.eclipse.jgit.internal.storage.reftable.ReftableConstants.FILE_HEADER_LEN;
@@ -108,6 +109,8 @@ public class ReftableWriter {
 	private ReftableOutputStream out;
 	private ObjectIdSubclassMap<RefList> obj2ref;
 
+	private BlockWriter.Entry lastRef;
+	private BlockWriter.Entry lastLog;
 	private BlockWriter cur;
 	private Section refs;
 	private Section objs;
@@ -120,6 +123,8 @@ public class ReftableWriter {
 	 */
 	public ReftableWriter() {
 		this(new ReftableConfig());
+		lastRef = null;
+		lastLog = null;
 	}
 
 	/**
@@ -269,10 +274,22 @@ public class ReftableWriter {
 			throw new IllegalArgumentException();
 		}
 		long d = updateIndex - minUpdateIndex;
-		long blockPos = refs.write(new RefEntry(ref, d));
+		RefEntry entry = new RefEntry(ref, d);
+		if (lastRef != null && Entry.compare(lastRef, entry) >= 0) {
+			throwIllegalEntry(lastRef, entry);
+		}
+		lastRef = entry;
+
+		long blockPos = refs.write(entry);
 		indexRef(ref, blockPos);
 	}
 
+	private void throwIllegalEntry(Entry last, Entry now) {
+		throw new IllegalArgumentException(
+			String.format("records must be increasing: last %s, this %s",
+				new String(last.key, UTF_8), new String(now.key, UTF_8)));
+	}
+
 	private void indexRef(Ref ref, long blockPos) {
 		if (indexObjects && !ref.isSymbolic()) {
 			indexId(ref.getObjectId(), blockPos);
@@ -322,7 +339,12 @@ public class ReftableWriter {
 					throws IOException {
 		String msg = message != null ? message : ""; //$NON-NLS-1$
 		beginLog();
-		logs.write(new LogEntry(ref, updateIndex, who, oldId, newId, msg));
+		LogEntry entry = new LogEntry(ref, updateIndex, who, oldId, newId, msg);
+		if (lastLog != null && Entry.compare(lastLog, entry) >= 0) {
+			throwIllegalEntry(lastLog, entry);
+		}
+		lastLog = entry;
+		logs.write(entry);
 	}
 
 	/**