Write reflog for refs/meta/config changes

A reflog is currently only written for branches under refs/heads/.
The refs/meta/config branch has no reflog, but it contains important
information such as access rights, and hence it should have a reflog
as well.

A problem with getting a reflog for refs/meta/config is that JGit
(and also native Git) is not creating a reflog for this branch even
if core.logAllRefUpdates is set (see section 'core.logAllRefUpdates'
in [1]).

To make JGit write the reflog for the refs/meta/config branch the
reflog file for this branch must already exist. This is why the
LocalDiskRepositoryManager now creates an empty reflog file for
the refs/meta/config branch when a new repository is created.

In addition this change contains a schema migration that creates the
reflog file for the refs/meta/config branch in all existing
repositories, so that further updates get a reflog entry. This
migration is only possible if the repositories are stored on local
disk and is not executed if a GitRepositoryManager other than
LocalDiskRepositoryManager is used.

[1] https://www.kernel.org/pub/software/scm/git/docs/git-config.html#_variables

Change-Id: I9b6354cfa51263db10fb99e329b397b86f40156d
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>

gerrit-server/src/main/java/com/google/gerrit/server/git/LocalDiskRepositoryManager.java

@@ -20,6 +20,7 @@ import com.google.common.base.MoreObjects;
 import com.google.gerrit.extensions.events.LifecycleListener;
 import com.google.gerrit.lifecycle.LifecycleModule;
 import com.google.gerrit.reviewdb.client.Project;
+import com.google.gerrit.reviewdb.client.RefNames;
 import com.google.gerrit.server.config.GerritServerConfig;
 import com.google.gerrit.server.config.SitePaths;
 import com.google.gerrit.server.notedb.NotesMigration;
@@ -246,6 +247,18 @@ public class LocalDiskRepositoryManager implements GitRepositoryManager {
         null, ConfigConstants.CONFIG_KEY_LOGALLREFUPDATES, true);
       config.save();
 
+      // JGit only writes to the reflog for refs/meta/config if the log file
+      // already exists.
+      //
+      File metaConfigLog =
+          new File(db.getDirectory(), "logs/" + RefNames.REFS_CONFIG);
+      if (!metaConfigLog.getParentFile().mkdirs()
+          || !metaConfigLog.createNewFile()) {
+        log.error(String.format(
+            "Failed to create ref log for %s in repository %s",
+            RefNames.REFS_CONFIG, name));
+      }
+
       onCreateProject(name);
 
       return db;

gerrit-server/src/main/java/com/google/gerrit/server/git/VersionedMetaData.java

@@ -45,7 +45,9 @@ import org.eclipse.jgit.transport.ReceiveCommand;
 import org.eclipse.jgit.treewalk.TreeWalk;
 import org.eclipse.jgit.util.RawParseUtils;
 
+import java.io.BufferedReader;
 import java.io.IOException;
+import java.io.StringReader;
 import java.util.Objects;
 
 /**
@@ -342,7 +344,12 @@ public abstract class VersionedMetaData {
         RefUpdate ru = db.updateRef(refName);
         ru.setExpectedOldObjectId(oldId);
         ru.setNewObjectId(src);
-        ru.disableRefLog();
+        ru.setRefLogIdent(update.getCommitBuilder().getAuthor());
+        try (BufferedReader reader = new BufferedReader(
+            new StringReader(update.getCommitBuilder().getMessage()))) {
+          // read the subject line and use it as reflog message
+          ru.setRefLogMessage("commit: " + reader.readLine(), true);
+        }
         inserter.flush();
         RefUpdate.Result result = ru.update();
         switch (result) {

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_105> C = Schema_105.class;
+  public static final Class<Schema_106> C = Schema_106.class;
 
   public static int getBinaryVersion() {
     return guessVersion(C);

gerrit-server/src/main/java/com/google/gerrit/server/schema/Schema_106.java

@@ -0,0 +1,104 @@
+// Copyright (C) 2015 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 static java.nio.charset.StandardCharsets.UTF_8;
+
+import com.google.gerrit.reviewdb.client.Project;
+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.git.GitRepositoryManager;
+import com.google.gerrit.server.git.LocalDiskRepositoryManager;
+import com.google.gwtorm.server.OrmException;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+
+import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.PersonIdent;
+import org.eclipse.jgit.lib.Repository;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.util.SortedSet;
+
+public class Schema_106 extends SchemaVersion {
+  private final GitRepositoryManager repoManager;
+  private final PersonIdent serverUser;
+
+  @Inject
+  Schema_106(Provider<Schema_105> prior,
+      GitRepositoryManager repoManager,
+      @GerritPersonIdent PersonIdent serverUser) {
+    super(prior);
+    this.repoManager = repoManager;
+    this.serverUser = serverUser;
+  }
+
+  @Override
+  protected void migrateData(ReviewDb db, UpdateUI ui) throws OrmException {
+    if (!(repoManager instanceof LocalDiskRepositoryManager)) {
+      return;
+    }
+
+    ui.message("listing all repositories ...");
+    SortedSet<Project.NameKey> repoList = repoManager.list();
+    ui.message("done");
+
+    ui.message(String.format("creating reflog files for %s branches ...",
+        RefNames.REFS_CONFIG));
+    for (Project.NameKey project : repoList) {
+      try {
+        Repository repo = repoManager.openRepository(project);
+        try {
+          File metaConfigLog =
+              new File(repo.getDirectory(), "logs/" + RefNames.REFS_CONFIG);
+          if (metaConfigLog.exists()) {
+            continue;
+          }
+
+          if (!metaConfigLog.getParentFile().mkdirs()
+              || !metaConfigLog.createNewFile()) {
+            throw new IOException(String.format(
+                "Failed to create reflog for %s in repository %s",
+                RefNames.REFS_CONFIG, project));
+          }
+
+          ObjectId metaConfigId = repo.resolve(RefNames.REFS_CONFIG);
+          if (metaConfigId != null) {
+            try (PrintWriter writer =
+                new PrintWriter(metaConfigLog, UTF_8.name())) {
+              writer.print(ObjectId.zeroId().name());
+              writer.print(" ");
+              writer.print(metaConfigId.name());
+              writer.print(" ");
+              writer.print(serverUser.toExternalString());
+              writer.print("\t");
+              writer.print("create reflog");
+              writer.println();
+            }
+          }
+        } finally {
+          repo.close();
+        }
+      } catch (IOException e) {
+        ui.message(String.format("ERROR: Failed to create reflog file for the"
+            + " %s branch in repository %s", RefNames.REFS_CONFIG, project.get()));
+      }
+    }
+    ui.message("done");
+  }
+}