Migrate starred changes to git (part 2)

This is the second part of migrating the starred changes from database
to git.

This change:
* bumps the database schema version
* migrates the starred changes from database to git (for single
  instance Gerrit servers)
* deletes the database table
* deletes the user.readStarredChangesFromGit config option

Change-Id: I534e98dc60050c5e409765c96def359503529035
Signed-off-by: Edwin Kempin <ekempin@google.com>

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

@@ -32,7 +32,7 @@ import java.util.List;
 /** A version of the database schema. */
 public abstract class SchemaVersion {
   /** The current schema version. */
-  public static final Class<Schema_122> C = Schema_122.class;
+  public static final Class<Schema_123> C = Schema_123.class;
 
   public static int getBinaryVersion() {
     return guessVersion(C);

gerrit-server/src/main/java/com/google/gerrit/server/schema/Schema_123.java

@@ -0,0 +1,92 @@
+// Copyright (C) 2016 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.common.collect.ArrayListMultimap;
+import com.google.common.collect.Multimap;
+import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.Change;
+import com.google.gerrit.reviewdb.client.RefNames;
+import com.google.gerrit.reviewdb.server.ReviewDb;
+import com.google.gerrit.server.StarredChangesUtil;
+import com.google.gerrit.server.config.AllUsersName;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gwtorm.jdbc.JdbcSchema;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+
+import org.eclipse.jgit.lib.BatchRefUpdate;
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.Repository;
+import org.eclipse.jgit.lib.TextProgressMonitor;
+import org.eclipse.jgit.revwalk.RevWalk;
+import org.eclipse.jgit.transport.ReceiveCommand;
+
+import java.io.IOException;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.util.Map;
+
+public class Schema_123 extends SchemaVersion {
+  private final GitRepositoryManager repoManager;
+  private final AllUsersName allUsersName;
+
+  @Inject
+  Schema_123(Provider<Schema_122> prior,
+      GitRepositoryManager repoManager,
+      AllUsersName allUsersName) {
+    super(prior);
+    this.repoManager = repoManager;
+    this.allUsersName = allUsersName;
+  }
+
+  @Override
+  protected void migrateData(ReviewDb db, UpdateUI ui)
+      throws OrmException, SQLException {
+    Multimap<Account.Id, Change.Id> imports = ArrayListMultimap.create();
+    try (Statement stmt = ((JdbcSchema) db).getConnection().createStatement();
+      ResultSet rs = stmt.executeQuery(
+          "SELECT "
+          + "account_id, "
+          + "change_id "
+          + "FROM starred_changes")) {
+      while (rs.next()) {
+        Account.Id accountId = new Account.Id(rs.getInt(1));
+        Change.Id changeId = new Change.Id(rs.getInt(2));
+        imports.put(accountId, changeId);
+      }
+    }
+
+    if (imports.isEmpty()) {
+      return;
+    }
+
+    try (Repository git = repoManager.openRepository(allUsersName);
+        RevWalk rw = new RevWalk(git)) {
+      BatchRefUpdate bru = git.getRefDatabase().newBatchUpdate();
+      ObjectId id = StarredChangesUtil.writeLabels(git,
+          StarredChangesUtil.DEFAULT_LABELS);
+      for (Map.Entry<Account.Id, Change.Id> e : imports.entries()) {
+        bru.addCommand(new ReceiveCommand(ObjectId.zeroId(), id,
+            RefNames.refsStarredChanges(e.getValue(), e.getKey())));
+      }
+      bru.execute(rw, new TextProgressMonitor());
+    } catch (IOException ex) {
+      throw new OrmException(ex);
+    }
+  }
+}