Merge "Create a user branch for every account"

gerrit-acceptance-framework/src/test/java/com/google/gerrit/acceptance/AccountCreator.java

@@ -53,7 +53,7 @@ public class AccountCreator {
   private final Map<String, TestAccount> accounts;
 
   private final SchemaFactory<ReviewDb> reviewDbProvider;
-  private final AccountsUpdate accountsUpdate;
+  private final AccountsUpdate.Server accountsUpdate;
   private final VersionedAuthorizedKeys.Accessor authorizedKeys;
   private final GroupCache groupCache;
   private final SshKeyCache sshKeyCache;
@@ -65,7 +65,7 @@ public class AccountCreator {
   @Inject
   AccountCreator(
       SchemaFactory<ReviewDb> schema,
-      AccountsUpdate accountsUpdate,
+      AccountsUpdate.Server accountsUpdate,
       VersionedAuthorizedKeys.Accessor authorizedKeys,
       GroupCache groupCache,
       SshKeyCache sshKeyCache,
@@ -114,7 +114,7 @@ public class AccountCreator {
       Account a = new Account(id, TimeUtil.nowTs());
       a.setFullName(fullName);
       a.setPreferredEmail(email);
-      accountsUpdate.insert(db, a);
+      accountsUpdate.create().insert(db, a);
 
       if (groups != null) {
         for (String n : groups) {

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/api/accounts/AccountIT.java

@@ -51,7 +51,6 @@ import com.google.gerrit.extensions.api.accounts.EmailInput;
 import com.google.gerrit.extensions.api.changes.AddReviewerInput;
 import com.google.gerrit.extensions.api.changes.ReviewInput;
 import com.google.gerrit.extensions.api.changes.StarsInput;
-import com.google.gerrit.extensions.client.GeneralPreferencesInfo;
 import com.google.gerrit.extensions.common.AccountInfo;
 import com.google.gerrit.extensions.common.ChangeInfo;
 import com.google.gerrit.extensions.common.GpgKeyInfo;
@@ -74,6 +73,7 @@ import com.google.gerrit.server.account.externalids.ExternalIds;
 import com.google.gerrit.server.account.externalids.ExternalIdsUpdate;
 import com.google.gerrit.server.config.AllUsersName;
 import com.google.gerrit.server.git.ProjectConfig;
+import com.google.gerrit.server.notedb.rebuild.ChangeRebuilderImpl;
 import com.google.gerrit.server.project.RefPattern;
 import com.google.gerrit.server.util.MagicBranch;
 import com.google.gerrit.testutil.ConfigSuite;
@@ -100,6 +100,8 @@ import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.Ref;
 import org.eclipse.jgit.lib.RefUpdate;
 import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.transport.PushCertificateIdent;
 import org.eclipse.jgit.transport.PushResult;
 import org.eclipse.jgit.transport.RemoteRefUpdate;
@@ -183,6 +185,26 @@ public class AccountIT extends AbstractDaemonTest {
     }
   }
 
+  @Test
+  public void create() throws Exception {
+    TestAccount foo = accounts.create("foo");
+    AccountInfo info = gApi.accounts().id(foo.id.get()).get();
+    assertThat(info.username).isEqualTo("foo");
+
+    // check user branch
+    try (Repository repo = repoManager.openRepository(allUsers);
+        RevWalk rw = new RevWalk(repo)) {
+      Ref ref = repo.exactRef(RefNames.refsUsers(foo.getId()));
+      assertThat(ref).isNotNull();
+      RevCommit c = rw.parseCommit(ref.getObjectId());
+      long timestampDiffMs =
+          Math.abs(
+              c.getCommitTime() * 1000L
+                  - accountCache.get(foo.getId()).getAccount().getRegisteredOn().getTime());
+      assertThat(timestampDiffMs).isAtMost(ChangeRebuilderImpl.MAX_WINDOW_MS);
+    }
+  }
+
   @Test
   public void get() throws Exception {
     AccountInfo info = gApi.accounts().id("admin").get();
@@ -553,7 +575,7 @@ public class AccountIT extends AbstractDaemonTest {
   @Test
   @Sandboxed
   public void fetchUserBranch() throws Exception {
-    ensureUserBranchCreated(user);
+    setApiUser(user);
 
     TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers, user);
     String userRefName = RefNames.refsUsers(user.id);
@@ -603,8 +625,6 @@ public class AccountIT extends AbstractDaemonTest {
 
   @Test
   public void pushToUserBranch() throws Exception {
-    ensureUserBranchCreated(admin);
-
     TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
     fetch(allUsersRepo, RefNames.refsUsers(admin.id) + ":userRef");
     allUsersRepo.reset("userRef");
@@ -617,8 +637,6 @@ public class AccountIT extends AbstractDaemonTest {
 
   @Test
   public void pushToUserBranchForReview() throws Exception {
-    ensureUserBranchCreated(admin);
-
     String userRefName = RefNames.refsUsers(admin.id);
     TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
     fetch(allUsersRepo, userRefName + ":userRef");
@@ -640,8 +658,6 @@ public class AccountIT extends AbstractDaemonTest {
 
   @Test
   public void pushWatchConfigToUserBranch() throws Exception {
-    ensureUserBranchCreated(admin);
-
     TestRepository<InMemoryRepository> allUsersRepo = cloneProject(allUsers);
     fetch(allUsersRepo, RefNames.refsUsers(admin.id) + ":userRef");
     allUsersRepo.reset("userRef");
@@ -683,8 +699,6 @@ public class AccountIT extends AbstractDaemonTest {
   @Test
   @Sandboxed
   public void cannotDeleteUserBranch() throws Exception {
-    ensureUserBranchCreated(admin);
-
     grant(
         Permission.DELETE,
         allUsers,
@@ -707,8 +721,6 @@ public class AccountIT extends AbstractDaemonTest {
   @Test
   @Sandboxed
   public void deleteUserBranchWithAccessDatabaseCapability() throws Exception {
-    ensureUserBranchCreated(admin);
-
     allowGlobalCapabilities(REGISTERED_USERS, GlobalCapability.ACCESS_DATABASE);
     grant(
         Permission.DELETE,
@@ -1019,12 +1031,4 @@ public class AccountIT extends AbstractDaemonTest {
     assertThat(accounts).hasSize(1);
     assertThat(Iterables.getOnlyElement(accounts)).isEqualTo(expectedAccount.getId());
   }
-
-  private void ensureUserBranchCreated(TestAccount account) throws Exception {
-    // Change something in the user preferences to ensure that the user branch is created.
-    setApiUser(account);
-    GeneralPreferencesInfo input = new GeneralPreferencesInfo();
-    input.changesPerPage = GeneralPreferencesInfo.defaults().changesPerPage + 10;
-    gApi.accounts().self().setPreferences(input);
-  }
 }

gerrit-pgm/src/main/java/com/google/gerrit/pgm/init/AccountsOnInit.java

@@ -0,0 +1,68 @@
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.pgm.init;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.gerrit.pgm.init.api.InitFlags;
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.GerritPersonIdentProvider;
+import com.google.gerrit.server.account.AccountsUpdate;
+import com.google.gerrit.server.config.SitePaths;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Path;
+import org.eclipse.jgit.internal.storage.file.FileRepository;
+import org.eclipse.jgit.lib.ObjectInserter;
+import org.eclipse.jgit.lib.PersonIdent;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.lib.RepositoryCache.FileKey;
+import org.eclipse.jgit.util.FS;
+
+public class AccountsOnInit {
+  private final InitFlags flags;
+  private final SitePaths site;
+  private final String allUsers;
+
+  @Inject
+  public AccountsOnInit(InitFlags flags, SitePaths site, AllUsersNameOnInitProvider allUsers) {
+    this.flags = flags;
+    this.site = site;
+    this.allUsers = allUsers.get();
+  }
+
+  public void insert(ReviewDb db, Account account) throws OrmException, IOException {
+    db.accounts().insert(ImmutableSet.of(account));
+
+    File path = getPath();
+    if (path != null) {
+      try (Repository repo = new FileRepository(path);
+          ObjectInserter oi = repo.newObjectInserter()) {
+        PersonIdent serverIdent = new GerritPersonIdentProvider(flags.cfg).get();
+        AccountsUpdate.createUserBranch(repo, oi, serverIdent, serverIdent, account);
+      }
+    }
+  }
+
+  private File getPath() {
+    Path basePath = site.resolve(flags.cfg.getString("gerrit", null, "basePath"));
+    checkArgument(basePath != null, "gerrit.basePath must be configured");
+    return FileKey.resolve(basePath.resolve(allUsers).toFile(), FS.DETECTED);
+  }
+}

gerrit-pgm/src/main/java/com/google/gerrit/pgm/init/InitAdminUser.java

@@ -29,7 +29,6 @@ import com.google.gerrit.reviewdb.client.AccountGroupName;
 import com.google.gerrit.reviewdb.client.AccountSshKey;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.account.AccountState;
-import com.google.gerrit.server.account.AccountsUpdate;
 import com.google.gerrit.server.account.externalids.ExternalId;
 import com.google.gerrit.server.index.account.AccountIndex;
 import com.google.gerrit.server.index.account.AccountIndexCollection;
@@ -48,7 +47,7 @@ import org.apache.commons.validator.routines.EmailValidator;
 public class InitAdminUser implements InitStep {
   private final ConsoleUI ui;
   private final InitFlags flags;
-  private final AccountsUpdate accountsUpdate;
+  private final AccountsOnInit accounts;
   private final VersionedAuthorizedKeysOnInit.Factory authorizedKeysFactory;
   private final ExternalIdsOnInit externalIds;
   private SchemaFactory<ReviewDb> dbFactory;
@@ -58,12 +57,12 @@ public class InitAdminUser implements InitStep {
   InitAdminUser(
       InitFlags flags,
       ConsoleUI ui,
-      AccountsUpdate accountsUpdate,
+      AccountsOnInit accounts,
       VersionedAuthorizedKeysOnInit.Factory authorizedKeysFactory,
       ExternalIdsOnInit externalIds) {
     this.flags = flags;
     this.ui = ui;
-    this.accountsUpdate = accountsUpdate;
+    this.accounts = accounts;
     this.authorizedKeysFactory = authorizedKeysFactory;
     this.externalIds = externalIds;
   }
@@ -110,7 +109,7 @@ public class InitAdminUser implements InitStep {
           Account a = new Account(id, TimeUtil.nowTs());
           a.setFullName(name);
           a.setPreferredEmail(email);
-          accountsUpdate.insert(db, a);
+          accounts.insert(db, a);
 
           AccountGroupName adminGroupName =
               db.accountGroupNames().get(new AccountGroup.NameKey("Administrators"));

gerrit-server/src/main/java/com/google/gerrit/server/account/AccountManager.java

@@ -52,6 +52,7 @@ public class AccountManager {
   private static final Logger log = LoggerFactory.getLogger(AccountManager.class);
 
   private final SchemaFactory<ReviewDb> schema;
+  private final AccountsUpdate.Server accountsUpdateFactory;
   private final AccountCache byIdCache;
   private final AccountByEmailCache byEmailCache;
   private final Realm realm;
@@ -67,6 +68,7 @@ public class AccountManager {
   @Inject
   AccountManager(
       SchemaFactory<ReviewDb> schema,
+      AccountsUpdate.Server accountsUpdateFactory,
       AccountCache byIdCache,
       AccountByEmailCache byEmailCache,
       Realm accountMapper,
@@ -78,6 +80,7 @@ public class AccountManager {
       ExternalIds externalIds,
       ExternalIdsUpdate.Server externalIdsUpdateFactory) {
     this.schema = schema;
+    this.accountsUpdateFactory = accountsUpdateFactory;
     this.byIdCache = byIdCache;
     this.byEmailCache = byEmailCache;
     this.realm = accountMapper;
@@ -229,7 +232,7 @@ public class AccountManager {
         awaitsFirstAccountCheck.getAndSet(false) && db.accounts().anyAccounts().toList().isEmpty();
 
     try {
-      db.accounts().upsert(Collections.singleton(account));
+      accountsUpdateFactory.create().upsert(db, account);
 
       ExternalId existingExtId = externalIds.get(db, extId.key());
       if (existingExtId != null && !existingExtId.accountId().equals(extId.accountId())) {

gerrit-server/src/main/java/com/google/gerrit/server/account/AccountsUpdate.java

@@ -14,22 +14,199 @@
 
 package com.google.gerrit.server.account;
 
+import static com.google.common.base.Preconditions.checkNotNull;
+
 import com.google.common.collect.ImmutableSet;
 import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.RefNames;
 import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.GerritPersonIdent;
+import com.google.gerrit.server.IdentifiedUser;
+import com.google.gerrit.server.config.AllUsersName;
+import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gwtorm.server.OrmDuplicateKeyException;
 import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
 import com.google.inject.Singleton;
+import java.io.IOException;
+import java.sql.Timestamp;
+import org.eclipse.jgit.lib.CommitBuilder;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectInserter;
+import org.eclipse.jgit.lib.PersonIdent;
+import org.eclipse.jgit.lib.RefUpdate;
+import org.eclipse.jgit.lib.RefUpdate.Result;
+import org.eclipse.jgit.lib.Repository;
 
 /** Updates accounts. */
 @Singleton
 public class AccountsUpdate {
+  /**
+   * Factory to create an AccountsUpdate instance for updating accounts by the Gerrit server.
+   *
+   * <p>The Gerrit server identity will be used as author and committer for all commits that update
+   * the accounts.
+   */
+  @Singleton
+  public static class Server {
+    private final GitRepositoryManager repoManager;
+    private final AllUsersName allUsersName;
+    private final Provider<PersonIdent> serverIdent;
+
+    @Inject
+    public Server(
+        GitRepositoryManager repoManager,
+        AllUsersName allUsersName,
+        @GerritPersonIdent Provider<PersonIdent> serverIdent) {
+      this.repoManager = repoManager;
+      this.allUsersName = allUsersName;
+      this.serverIdent = serverIdent;
+    }
+
+    public AccountsUpdate create() {
+      PersonIdent i = serverIdent.get();
+      return new AccountsUpdate(repoManager, allUsersName, i, i);
+    }
+  }
+
+  /**
+   * Factory to create an AccountsUpdate instance for updating accounts by the current user.
+   *
+   * <p>The identity of the current user will be used as author for all commits that update the
+   * accounts. The Gerrit server identity will be used as committer.
+   */
+  @Singleton
+  public static class User {
+    private final GitRepositoryManager repoManager;
+    private final AllUsersName allUsersName;
+    private final Provider<PersonIdent> serverIdent;
+    private final Provider<IdentifiedUser> identifiedUser;
+
+    @Inject
+    public User(
+        GitRepositoryManager repoManager,
+        AllUsersName allUsersName,
+        @GerritPersonIdent Provider<PersonIdent> serverIdent,
+        Provider<IdentifiedUser> identifiedUser) {
+      this.repoManager = repoManager;
+      this.allUsersName = allUsersName;
+      this.serverIdent = serverIdent;
+      this.identifiedUser = identifiedUser;
+    }
+
+    public AccountsUpdate create() {
+      PersonIdent i = serverIdent.get();
+      return new AccountsUpdate(
+          repoManager, allUsersName, createPersonIdent(i, identifiedUser.get()), i);
+    }
+
+    private PersonIdent createPersonIdent(PersonIdent ident, IdentifiedUser user) {
+      return user.newCommitterIdent(ident.getWhen(), ident.getTimeZone());
+    }
+  }
+
+  private final GitRepositoryManager repoManager;
+  private final AllUsersName allUsersName;
+  private final PersonIdent committerIdent;
+  private final PersonIdent authorIdent;
+
+  private AccountsUpdate(
+      GitRepositoryManager repoManager,
+      AllUsersName allUsersName,
+      PersonIdent committerIdent,
+      PersonIdent authorIdent) {
+    this.repoManager = checkNotNull(repoManager, "repoManager");
+    this.allUsersName = checkNotNull(allUsersName, "allUsersName");
+    this.committerIdent = checkNotNull(committerIdent, "committerIdent");
+    this.authorIdent = checkNotNull(authorIdent, "authorIdent");
+  }
+
   /**
    * Inserts a new account.
    *
    * @throws OrmDuplicateKeyException if the account already exists
+   * @throws IOException if updating the user branch fails
    */
-  public void insert(ReviewDb db, Account account) throws OrmException {
+  public void insert(ReviewDb db, Account account) throws OrmException, IOException {
     db.accounts().insert(ImmutableSet.of(account));
+    createUserBranch(account);
+  }
+
+  /**
+   * Inserts or updates an account.
+   *
+   * <p>If the account already exists, it is overwritten, otherwise it is inserted.
+   */
+  public void upsert(ReviewDb db, Account account) throws OrmException, IOException {
+    db.accounts().upsert(ImmutableSet.of(account));
+    createUserBranchIfNeeded(account);
+  }
+
+  private void createUserBranch(Account account) throws IOException {
+    try (Repository repo = repoManager.openRepository(allUsersName);
+        ObjectInserter oi = repo.newObjectInserter()) {
+      String refName = RefNames.refsUsers(account.getId());
+      if (repo.exactRef(refName) != null) {
+        throw new IOException(
+            String.format(
+                "User branch %s for newly created account %s already exists.",
+                refName, account.getId().get()));
+      }
+      createUserBranch(repo, oi, committerIdent, authorIdent, account);
+    }
+  }
+
+  private void createUserBranchIfNeeded(Account account) throws IOException {
+    try (Repository repo = repoManager.openRepository(allUsersName);
+        ObjectInserter oi = repo.newObjectInserter()) {
+      if (repo.exactRef(RefNames.refsUsers(account.getId())) == null) {
+        createUserBranch(repo, oi, committerIdent, authorIdent, account);
+      }
+    }
+  }
+
+  public static void createUserBranch(
+      Repository repo,
+      ObjectInserter oi,
+      PersonIdent committerIdent,
+      PersonIdent authorIdent,
+      Account account)
+      throws IOException {
+    ObjectId id =
+        createInitialEmptyCommit(oi, committerIdent, authorIdent, account.getRegisteredOn());
+
+    String refName = RefNames.refsUsers(account.getId());
+    RefUpdate ru = repo.updateRef(refName);
+    ru.setExpectedOldObjectId(ObjectId.zeroId());
+    ru.setNewObjectId(id);
+    ru.setForceUpdate(true);
+    ru.setRefLogIdent(committerIdent);
+    ru.setRefLogMessage("Create Account", true);
+    Result result = ru.update();
+    if (result != Result.NEW) {
+      throw new IOException(String.format("Failed to update ref %s: %s", refName, result.name()));
+    }
+  }
+
+  private static ObjectId createInitialEmptyCommit(
+      ObjectInserter oi,
+      PersonIdent committerIdent,
+      PersonIdent authorIdent,
+      Timestamp registrationDate)
+      throws IOException {
+    CommitBuilder cb = new CommitBuilder();
+    cb.setTreeId(emptyTree(oi));
+    cb.setCommitter(new PersonIdent(committerIdent, registrationDate));
+    cb.setAuthor(new PersonIdent(authorIdent, registrationDate));
+    cb.setMessage("Create Account");
+    ObjectId id = oi.insert(cb);
+    oi.flush();
+    return id;
+  }
+
+  private static ObjectId emptyTree(ObjectInserter oi) throws IOException {
+    return oi.insert(Constants.OBJ_TREE, new byte[] {});
   }
 }

gerrit-server/src/main/java/com/google/gerrit/server/account/CreateAccount.java

@@ -69,7 +69,7 @@ public class CreateAccount implements RestModifyView<TopLevelResource, AccountIn
   private final VersionedAuthorizedKeys.Accessor authorizedKeys;
   private final SshKeyCache sshKeyCache;
   private final AccountCache accountCache;
-  private final AccountsUpdate accountsUpdate;
+  private final AccountsUpdate.User accountsUpdate;
   private final AccountIndexer indexer;
   private final AccountByEmailCache byEmailCache;
   private final AccountLoader.Factory infoLoader;
@@ -87,7 +87,7 @@ public class CreateAccount implements RestModifyView<TopLevelResource, AccountIn
       VersionedAuthorizedKeys.Accessor authorizedKeys,
       SshKeyCache sshKeyCache,
       AccountCache accountCache,
-      AccountsUpdate accountsUpdate,
+      AccountsUpdate.User accountsUpdate,
       AccountIndexer indexer,
       AccountByEmailCache byEmailCache,
       AccountLoader.Factory infoLoader,
@@ -175,7 +175,7 @@ public class CreateAccount implements RestModifyView<TopLevelResource, AccountIn
     Account a = new Account(id, TimeUtil.nowTs());
     a.setFullName(input.name);
     a.setPreferredEmail(input.email);
-    accountsUpdate.insert(db, a);
+    accountsUpdate.create().insert(db, a);
 
     for (AccountGroup.Id groupId : groups) {
       AccountGroupMember m = new AccountGroupMember(new AccountGroupMember.Key(id, groupId));

gerrit-server/src/main/java/com/google/gerrit/server/schema/SchemaVersion.java

@@ -35,7 +35,7 @@ import java.util.concurrent.TimeUnit;
 /** A version of the database schema. */
 public abstract class SchemaVersion {
   /** The current schema version. */
-  public static final Class<Schema_145> C = Schema_145.class;
+  public static final Class<Schema_146> C = Schema_146.class;
 
   public static int getBinaryVersion() {
     return guessVersion(C);

gerrit-server/src/main/java/com/google/gerrit/server/schema/Schema_146.java

@@ -0,0 +1,156 @@
+// Copyright (C) 2017 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.google.gerrit.server.schema;
+
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.RefNames;
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.GerritPersonIdent;
+import com.google.gerrit.server.account.AccountsUpdate;
+import com.google.gerrit.server.config.AllUsersName;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+import java.io.IOException;
+import java.sql.SQLException;
+import java.sql.Timestamp;
+import org.eclipse.jgit.lib.CommitBuilder;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.ObjectInserter;
+import org.eclipse.jgit.lib.PersonIdent;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.lib.RefUpdate;
+import org.eclipse.jgit.lib.RefUpdate.Result;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevSort;
+import org.eclipse.jgit.revwalk.RevWalk;
+
+/**
+ * Make sure that for every account a user branch exists that has an initial empty commit with the
+ * registration date as commit time.
+ *
+ * <p>For accounts that don't have a user branch yet the user branch is created with an initial
+ * empty commit that has the registration date as commit time.
+ *
+ * <p>For accounts that already have a user branch the user branch is rewritten and an initial empty
+ * commit with the registration date as commit time is inserted (if such a commit doesn't exist
+ * yet).
+ */
+public class Schema_146 extends SchemaVersion {
+  private static final String CREATE_ACCOUNT_MSG = "Create Account";
+
+  private final GitRepositoryManager repoManager;
+  private final AllUsersName allUsersName;
+  private final PersonIdent serverIdent;
+
+  @Inject
+  Schema_146(
+      Provider<Schema_145> prior,
+      GitRepositoryManager repoManager,
+      AllUsersName allUsersName,
+      @GerritPersonIdent PersonIdent serverIdent) {
+    super(prior);
+    this.repoManager = repoManager;
+    this.allUsersName = allUsersName;
+    this.serverIdent = serverIdent;
+  }
+
+  @Override
+  protected void migrateData(ReviewDb db, UpdateUI ui) throws OrmException, SQLException {
+    try (Repository repo = repoManager.openRepository(allUsersName);
+        RevWalk rw = new RevWalk(repo);
+        ObjectInserter oi = repo.newObjectInserter()) {
+      ObjectId emptyTree = emptyTree(oi);
+
+      for (Account account : db.accounts().all()) {
+        String refName = RefNames.refsUsers(account.getId());
+        Ref ref = repo.exactRef(refName);
+        if (ref != null) {
+          rewriteUserBranch(repo, rw, oi, emptyTree, ref, account);
+        } else {
+          AccountsUpdate.createUserBranch(repo, oi, serverIdent, serverIdent, account);
+        }
+      }
+    } catch (IOException e) {
+      throw new OrmException("Failed to rewrite user branches.", e);
+    }
+  }
+
+  private void rewriteUserBranch(
+      Repository repo, RevWalk rw, ObjectInserter oi, ObjectId emptyTree, Ref ref, Account account)
+      throws IOException {
+    ObjectId current = createInitialEmptyCommit(oi, emptyTree, account.getRegisteredOn());
+
+    rw.reset();
+    rw.sort(RevSort.TOPO);
+    rw.sort(RevSort.REVERSE, true);
+    rw.markStart(rw.parseCommit(ref.getObjectId()));
+
+    RevCommit c;
+    while ((c = rw.next()) != null) {
+      if (isInitialEmptyCommit(emptyTree, c)) {
+        return;
+      }
+
+      CommitBuilder cb = new CommitBuilder();
+      cb.setParentId(current);
+      cb.setTreeId(c.getTree());
+      cb.setAuthor(c.getAuthorIdent());
+      cb.setCommitter(c.getCommitterIdent());
+      cb.setMessage(c.getFullMessage());
+      cb.setEncoding(c.getEncoding());
+      current = oi.insert(cb);
+    }
+
+    oi.flush();
+
+    RefUpdate ru = repo.updateRef(ref.getName());
+    ru.setExpectedOldObjectId(ref.getObjectId());
+    ru.setNewObjectId(current);
+    ru.setForceUpdate(true);
+    ru.setRefLogIdent(serverIdent);
+    ru.setRefLogMessage(getClass().getSimpleName(), true);
+    Result result = ru.update();
+    if (result != Result.FORCED) {
+      throw new IOException(
+          String.format("Failed to update ref %s: %s", ref.getName(), result.name()));
+    }
+  }
+
+  private ObjectId createInitialEmptyCommit(
+      ObjectInserter oi, ObjectId emptyTree, Timestamp registrationDate) throws IOException {
+    PersonIdent ident = new PersonIdent(serverIdent, registrationDate);
+
+    CommitBuilder cb = new CommitBuilder();
+    cb.setTreeId(emptyTree);
+    cb.setCommitter(ident);
+    cb.setAuthor(ident);
+    cb.setMessage(CREATE_ACCOUNT_MSG);
+    return oi.insert(cb);
+  }
+
+  private boolean isInitialEmptyCommit(ObjectId emptyTree, RevCommit c) {
+    return c.getParentCount() == 0
+        && c.getTree().equals(emptyTree)
+        && c.getShortMessage().equals(CREATE_ACCOUNT_MSG);
+  }
+
+  private static ObjectId emptyTree(ObjectInserter oi) throws IOException {
+    return oi.insert(Constants.OBJ_TREE, new byte[] {});
+  }
+}