create-project: Bring back --permissions-only flag

If a project is permissions only, assign HEAD to point to
refs/meta/config. This way gitweb view of the project shows the
permissions history by default, and clients that clone the project
are able to get a detached HEAD pointing to the current permission
state, rather than an empty repository.

Change-Id: I194bfef1af9d00268de9c503ea986879f1fbaff9

gerrit-server/src/main/java/com/google/gerrit/server/schema/Schema_56.java

@@ -0,0 +1,80 @@
+// Copyright (C) 2011 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.Project;
+import com.google.gerrit.reviewdb.ReviewDb;
+import com.google.gerrit.server.git.GitRepositoryManager;
+import com.google.gerrit.server.git.LocalDiskRepositoryManager;
+import com.google.inject.Inject;
+import com.google.inject.Provider;
+
+import org.eclipse.jgit.errors.RepositoryNotFoundException;
+import org.eclipse.jgit.lib.Constants;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.lib.RefUpdate;
+import org.eclipse.jgit.lib.Repository;
+
+import java.io.IOException;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+
+public class Schema_56 extends SchemaVersion {
+  private final LocalDiskRepositoryManager mgr;
+  private final Set<String> keysOne;
+  private final Set<String> keysTwo;
+
+  @Inject
+  Schema_56(Provider<Schema_55> prior, LocalDiskRepositoryManager mgr) {
+    super(prior);
+    this.mgr = mgr;
+
+    keysOne = new HashSet<String>();
+    keysTwo = new HashSet<String>();
+
+    keysOne.add(GitRepositoryManager.REF_CONFIG);
+    keysTwo.add(GitRepositoryManager.REF_CONFIG);
+    keysTwo.add(Constants.HEAD);
+  }
+
+  @Override
+  protected void migrateData(ReviewDb db, UpdateUI ui) {
+    for (Project.NameKey name : mgr.list()) {
+      Repository git;
+      try {
+        git = mgr.openRepository(name);
+      } catch (RepositoryNotFoundException e) {
+        ui.message("warning: Cannot open " + name.get());
+        continue;
+      }
+      try {
+        Map<String, Ref> all = git.getAllRefs();
+        if (all.keySet().equals(keysOne) || all.keySet().equals(keysTwo)) {
+          try {
+            RefUpdate update = git.updateRef(Constants.HEAD);
+            update.disableRefLog();
+            update.link(GitRepositoryManager.REF_CONFIG);
+          } catch (IOException err) {
+            ui.message("warning: " + name.get() + ": Cannot update HEAD to "
+                + GitRepositoryManager.REF_CONFIG + ": " + err.getMessage());
+          }
+        }
+      } finally {
+        git.close();
+      }
+    }
+  }
+}