Add UploadPackInitializer extension point

I suggested to Luca at the hackathon that he could use this mechanism to
limit refs advertised to Jenkins, instead of writing a custom
PermissionBackend. Getting this in 2.15 means people using his plugin
won't have to wait for the next release to stop using the
PermissionBackend hack.

Change-Id: I8c38eef94d6e505b926b3da6c470e34f6613ca2c

Documentation/dev-plugins.txt

@@ -500,6 +500,19 @@ notified when JGit successfully receives a pack. This may be useful
 for those plugins which would like to monitor changes in Git
 repositories.
 
+[[upload-pack]]
+== Upload Pack Initializers
+
+Plugins may provide UploadPackInitializer instances, which will be
+invoked by Gerrit just before a UploadPack instance will be used.
+Usually, plugins will make use of the setXXX methods on the UploadPack
+to set additional properties on it.
+
+The interactions with the core Gerrit UploadPack initialization and
+between UploadPackInitializers can be complex. Please read the
+UploadPack Javadoc and Gerrit Upload/UploadFactory implementations
+carefully.
+
 [[pre-upload-hook]]
 == Pre Upload-Pack Hooks
 

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

@@ -32,6 +32,7 @@ import com.google.gerrit.server.config.GerritRequestModule;
 import com.google.gerrit.server.config.RequestScopedReviewDbProvider;
 import com.google.gerrit.server.git.ReceivePackInitializer;
 import com.google.gerrit.server.git.TransferConfig;
+import com.google.gerrit.server.git.UploadPackInitializer;
 import com.google.gerrit.server.git.VisibleRefFilter;
 import com.google.gerrit.server.git.receive.AsyncReceiveCommits;
 import com.google.gerrit.server.git.validators.UploadValidators;
@@ -211,6 +212,7 @@ class InProcessProtocol extends TestProtocol<Context> {
     private final Provider<CurrentUser> userProvider;
     private final VisibleRefFilter.Factory refFilterFactory;
     private final TransferConfig transferConfig;
+    private final DynamicSet<UploadPackInitializer> uploadPackInitializers;
     private final DynamicSet<PreUploadHook> preUploadHooks;
     private final UploadValidators.Factory uploadValidatorsFactory;
     private final ThreadLocalRequestContext threadContext;
@@ -222,6 +224,7 @@ class InProcessProtocol extends TestProtocol<Context> {
         Provider<CurrentUser> userProvider,
         VisibleRefFilter.Factory refFilterFactory,
         TransferConfig transferConfig,
+        DynamicSet<UploadPackInitializer> uploadPackInitializers,
         DynamicSet<PreUploadHook> preUploadHooks,
         UploadValidators.Factory uploadValidatorsFactory,
         ThreadLocalRequestContext threadContext,
@@ -230,6 +233,7 @@ class InProcessProtocol extends TestProtocol<Context> {
       this.userProvider = userProvider;
       this.refFilterFactory = refFilterFactory;
       this.transferConfig = transferConfig;
+      this.uploadPackInitializers = uploadPackInitializers;
       this.preUploadHooks = preUploadHooks;
       this.uploadValidatorsFactory = uploadValidatorsFactory;
       this.threadContext = threadContext;
@@ -273,6 +277,9 @@ class InProcessProtocol extends TestProtocol<Context> {
       List<PreUploadHook> hooks = Lists.newArrayList(preUploadHooks);
       hooks.add(uploadValidatorsFactory.create(projectState.getProject(), repo, "localhost-test"));
       up.setPreUploadHook(PreUploadHookChain.newChain(hooks));
+      for (UploadPackInitializer initializer : uploadPackInitializers) {
+        initializer.init(req.project, up);
+      }
       return up;
     }
   }

gerrit-httpd/src/main/java/com/google/gerrit/httpd/GitOverHttpServlet.java

@@ -27,6 +27,7 @@ import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.cache.CacheModule;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.git.TransferConfig;
+import com.google.gerrit.server.git.UploadPackInitializer;
 import com.google.gerrit.server.git.VisibleRefFilter;
 import com.google.gerrit.server.git.receive.AsyncReceiveCommits;
 import com.google.gerrit.server.git.validators.UploadValidators;
@@ -209,15 +210,18 @@ public class GitOverHttpServlet extends GitServlet {
     private final TransferConfig config;
     private final DynamicSet<PreUploadHook> preUploadHooks;
     private final DynamicSet<PostUploadHook> postUploadHooks;
+    private final DynamicSet<UploadPackInitializer> uploadPackInitializers;
 
     @Inject
     UploadFactory(
         TransferConfig tc,
         DynamicSet<PreUploadHook> preUploadHooks,
-        DynamicSet<PostUploadHook> postUploadHooks) {
+        DynamicSet<PostUploadHook> postUploadHooks,
+        DynamicSet<UploadPackInitializer> uploadPackInitializers) {
       this.config = tc;
       this.preUploadHooks = preUploadHooks;
       this.postUploadHooks = postUploadHooks;
+      this.uploadPackInitializers = uploadPackInitializers;
     }
 
     @Override
@@ -227,6 +231,10 @@ public class GitOverHttpServlet extends GitServlet {
       up.setTimeout(config.getTimeout());
       up.setPreUploadHook(PreUploadHookChain.newChain(Lists.newArrayList(preUploadHooks)));
       up.setPostUploadHook(PostUploadHookChain.newChain(Lists.newArrayList(postUploadHooks)));
+      ProjectControl pc = (ProjectControl) req.getAttribute(ATT_CONTROL);
+      for (UploadPackInitializer initializer : uploadPackInitializers) {
+        initializer.init(pc.getProject().getNameKey(), up);
+      }
       return up;
     }
   }

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

@@ -0,0 +1,35 @@
+// 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.git;
+
+import com.google.gerrit.extensions.annotations.ExtensionPoint;
+import com.google.gerrit.reviewdb.client.Project;
+import org.eclipse.jgit.transport.UploadPack;
+
+@ExtensionPoint
+public interface UploadPackInitializer {
+
+  /**
+   * UploadPack initialization.
+   *
+   * <p>Invoked by Gerrit when a new UploadPack instance is created and just before it is used.
+   * Implementors will usually call setXXX methods on the uploadPack parameter in order to set
+   * additional properties on it.
+   *
+   * @param project project for which the UploadPack is created
+   * @param uploadPack the UploadPack instance which is being initialized
+   */
+  void init(Project.NameKey project, UploadPack uploadPack);
+}

gerrit-sshd/src/main/java/com/google/gerrit/sshd/commands/Upload.java

@@ -18,6 +18,7 @@ import com.google.common.collect.Lists;
 import com.google.gerrit.extensions.registration.DynamicSet;
 import com.google.gerrit.extensions.restapi.AuthException;
 import com.google.gerrit.server.git.TransferConfig;
+import com.google.gerrit.server.git.UploadPackInitializer;
 import com.google.gerrit.server.git.VisibleRefFilter;
 import com.google.gerrit.server.git.validators.UploadValidationException;
 import com.google.gerrit.server.git.validators.UploadValidators;
@@ -41,6 +42,7 @@ final class Upload extends AbstractGitCommand {
   @Inject private VisibleRefFilter.Factory refFilterFactory;
   @Inject private DynamicSet<PreUploadHook> preUploadHooks;
   @Inject private DynamicSet<PostUploadHook> postUploadHooks;
+  @Inject private DynamicSet<UploadPackInitializer> uploadPackInitializers;
   @Inject private UploadValidators.Factory uploadValidatorsFactory;
   @Inject private SshSession session;
   @Inject private PermissionBackend permissionBackend;
@@ -68,6 +70,9 @@ final class Upload extends AbstractGitCommand {
     allPreUploadHooks.add(
         uploadValidatorsFactory.create(project, repo, session.getRemoteAddressAsString()));
     up.setPreUploadHook(PreUploadHookChain.newChain(allPreUploadHooks));
+    for (UploadPackInitializer initializer : uploadPackInitializers) {
+      initializer.init(projectControl.getProject().getNameKey(), up);
+    }
     try {
       up.upload(in, out, err);
       session.setPeerAgent(up.getPeerUserAgent());