MetaDataUpdate: Make factories singletons

Typically factories are singletons, which means callers are tempted to
inject them directly instead of using providers, which would be the
correct thing to do in this case.

However, the only thing that is non-singleton-ish about them was that
they directly injected the @GerritPersonIdent; there's no need for this,
as they can inject a provider instead.

Change-Id: If7fbe2ccdc26a5cfc258efaf6495eb4ca7260b2d

java/com/google/gerrit/server/git/meta/MetaDataUpdate.java

@@ -22,6 +22,7 @@ import com.google.gerrit.server.extensions.events.GitReferenceUpdated;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.inject.Inject;
 import com.google.inject.Provider;
+import com.google.inject.Singleton;
 import com.google.inject.assistedinject.Assisted;
 import java.io.IOException;
 import org.eclipse.jgit.errors.RepositoryNotFoundException;
@@ -33,21 +34,22 @@ import org.eclipse.jgit.lib.Repository;
 
 /** Helps with the updating of a {@link VersionedMetaData}. */
 public class MetaDataUpdate implements AutoCloseable {
+  @Singleton
   public static class User {
     private final InternalFactory factory;
     private final GitRepositoryManager mgr;
-    private final PersonIdent serverIdent;
+    private final Provider<PersonIdent> serverIdentProvider;
     private final Provider<IdentifiedUser> identifiedUser;
 
     @Inject
     User(
         InternalFactory factory,
         GitRepositoryManager mgr,
-        @GerritPersonIdent PersonIdent serverIdent,
+        @GerritPersonIdent Provider<PersonIdent> serverIdentProvider,
         Provider<IdentifiedUser> identifiedUser) {
       this.factory = factory;
       this.mgr = mgr;
-      this.serverIdent = serverIdent;
+      this.serverIdentProvider = serverIdentProvider;
       this.identifiedUser = identifiedUser;
     }
 
@@ -126,29 +128,31 @@ public class MetaDataUpdate implements AutoCloseable {
     public MetaDataUpdate create(
         Project.NameKey name, Repository repository, IdentifiedUser user, BatchRefUpdate batch) {
       MetaDataUpdate md = factory.create(name, repository, batch);
-      md.getCommitBuilder().setCommitter(serverIdent);
+      md.getCommitBuilder().setCommitter(serverIdentProvider.get());
       md.setAuthor(user);
       return md;
     }
 
     private PersonIdent createPersonIdent(IdentifiedUser user) {
+      PersonIdent serverIdent = serverIdentProvider.get();
       return user.newCommitterIdent(serverIdent.getWhen(), serverIdent.getTimeZone());
     }
   }
 
+  @Singleton
   public static class Server {
     private final InternalFactory factory;
     private final GitRepositoryManager mgr;
-    private final PersonIdent serverIdent;
+    private final Provider<PersonIdent> serverIdentProvider;
 
     @Inject
     Server(
         InternalFactory factory,
         GitRepositoryManager mgr,
-        @GerritPersonIdent PersonIdent serverIdent) {
+        @GerritPersonIdent Provider<PersonIdent> serverIdentProvider) {
       this.factory = factory;
       this.mgr = mgr;
-      this.serverIdent = serverIdent;
+      this.serverIdentProvider = serverIdentProvider;
     }
 
     public MetaDataUpdate create(Project.NameKey name)
@@ -162,6 +166,7 @@ public class MetaDataUpdate implements AutoCloseable {
       Repository repo = mgr.openRepository(name);
       MetaDataUpdate md = factory.create(name, repo, batch);
       md.setCloseRepository(true);
+      PersonIdent serverIdent = serverIdentProvider.get();
       md.getCommitBuilder().setAuthor(serverIdent);
       md.getCommitBuilder().setCommitter(serverIdent);
       return md;