Add merge validation interface

Add a new MergeValidationListener interface which can be used to
provide additional validation of commits before they are merged to
the git repository.

Add a MergeValidators class to invoke the merge validator listeners,
and call it from MergeOp before the commit is merged.

Add a listener to invoke validation provided by plugins.

Change-Id: I325d923f5cc0245b60e86a035329b640c1682d48

Documentation/config-validation.txt

@@ -4,6 +4,11 @@ Gerrit Code Review - Commit Validation
 Gerrit supports link:dev-plugins.html[plugin-based] validation of
 commits.
 
+[[new-commit-validation]]
+New commit validation
+---------------------
+
+
 Plugins implementing the `CommitValidationListener` interface can
 perform additional validation checks against new commits.
 
@@ -18,6 +23,18 @@ and cherry-pick buttons.
 Out of the box, Gerrit includes a plugin that checks the length of the
 subject and body lines of commit messages on uploaded commits.
 
+[[pre-merge-validation]]
+Pre-merge validation
+--------------------
+
+
+Plugins implementing the `MergeValidationListener` interface can
+perform additional validation checks against commits before they
+are merged to the git repository.
+
+If the commit fails the validation, the plugin can throw an exception
+which will cause the merge to fail.
+
 
 GERRIT
 ------

gerrit-server/src/main/java/com/google/gerrit/server/config/GerritGlobalModule.java

@@ -80,6 +80,8 @@ import com.google.gerrit.server.git.TagCache;
 import com.google.gerrit.server.git.TransferConfig;
 import com.google.gerrit.server.git.validators.CommitValidationListener;
 import com.google.gerrit.server.git.validators.CommitValidators;
+import com.google.gerrit.server.git.validators.MergeValidationListener;
+import com.google.gerrit.server.git.validators.MergeValidators;
 import com.google.gerrit.server.mail.AddReviewerSender;
 import com.google.gerrit.server.mail.CommitMessageEditedSender;
 import com.google.gerrit.server.mail.CreateChangeSender;
@@ -251,11 +253,13 @@ public class GerritGlobalModule extends FactoryModule {
     DynamicSet.bind(binder(), GitReferenceUpdatedListener.class).to(ChangeCache.class);
     DynamicSet.setOf(binder(), ChangeListener.class);
     DynamicSet.setOf(binder(), CommitValidationListener.class);
+    DynamicSet.setOf(binder(), MergeValidationListener.class);
     DynamicItem.itemOf(binder(), AvatarProvider.class);
 
     bind(AnonymousUser.class);
 
     factory(CommitValidators.Factory.class);
+    factory(MergeValidators.Factory.class);
     factory(NotesBranchUtil.Factory.class);
 
     bind(AccountManager.class);

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

@@ -43,6 +43,8 @@ import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.account.AccountCache;
 import com.google.gerrit.server.config.AllProjectsName;
 import com.google.gerrit.server.extensions.events.GitReferenceUpdated;
+import com.google.gerrit.server.git.validators.MergeValidationException;
+import com.google.gerrit.server.git.validators.MergeValidators;
 import com.google.gerrit.server.index.ChangeIndexer;
 import com.google.gerrit.server.mail.MergeFailSender;
 import com.google.gerrit.server.mail.MergedSender;
@@ -130,6 +132,7 @@ public class MergeOp {
   private final IdentifiedUser.GenericFactory identifiedUserFactory;
   private final ChangeControl.GenericFactory changeControlFactory;
   private final MergeQueue mergeQueue;
+  private final MergeValidators.Factory mergeValidatorsFactory;
 
   private final Branch.NameKey destBranch;
   private ProjectState destProject;
@@ -170,7 +173,8 @@ public class MergeOp {
       final WorkQueue workQueue,
       final RequestScopePropagator requestScopePropagator,
       final AllProjectsName allProjectsName,
-      final ChangeIndexer indexer) {
+      final ChangeIndexer indexer,
+      final MergeValidators.Factory mergeValidatorsFactory) {
     repoManager = grm;
     schemaFactory = sf;
     labelNormalizer = fs;
@@ -191,6 +195,7 @@ public class MergeOp {
     this.requestScopePropagator = requestScopePropagator;
     this.allProjectsName = allProjectsName;
     this.indexer = indexer;
+    this.mergeValidatorsFactory = mergeValidatorsFactory;
     destBranch = branch;
     toMerge = ArrayListMultimap.create();
     potentiallyStillSubmittable = new ArrayList<CodeReviewCommit>();
@@ -487,6 +492,14 @@ public class MergeOp {
         continue;
       }
 
+      MergeValidators mergeValidators = mergeValidatorsFactory.create();
+      try {
+        mergeValidators.validatePreMerge(repo, commit, destProject, destBranch, ps.getId());
+      } catch (MergeValidationException mve) {
+        commits.put(changeId, CodeReviewCommit.error(mve.getStatus()));
+        continue;
+      }
+
       if (GitRepositoryManager.REF_CONFIG.equals(destBranch.get())) {
         final Project.NameKey newParent;
         try {

gerrit-server/src/main/java/com/google/gerrit/server/git/validators/MergeValidationException.java

@@ -0,0 +1,31 @@
+// Copyright (C) 2013 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.validators;
+
+import com.google.gerrit.server.git.CommitMergeStatus;
+
+public class MergeValidationException extends Exception {
+  private static final long serialVersionUID = 1L;
+  private final CommitMergeStatus status;
+
+  public MergeValidationException(CommitMergeStatus status) {
+    super(status.toString());
+    this.status = status;
+  }
+
+  public CommitMergeStatus getStatus() {
+    return status;
+  }
+}

gerrit-server/src/main/java/com/google/gerrit/server/git/validators/MergeValidationListener.java

@@ -0,0 +1,48 @@
+// Copyright (C) 2013 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.validators;
+
+import com.google.gerrit.extensions.annotations.ExtensionPoint;
+import com.google.gerrit.reviewdb.client.Branch;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.server.git.CodeReviewCommit;
+import com.google.gerrit.server.project.ProjectState;
+
+import org.eclipse.jgit.lib.Repository;
+
+/**
+ * Listener to provide validation of commits before merging.
+ *
+ * Invoked by Gerrit before a commit is merged.
+ */
+@ExtensionPoint
+public interface MergeValidationListener {
+  /**
+   * Validate a commit before it is merged.
+   *
+   * @param repo the repository
+   * @param commit commit details
+   * @param destProject the destination project
+   * @param destBranch the destination branch
+   * @param patchSetId the patch set ID
+   * @throws MergeValidationException if the commit fails to validate
+   */
+  public void onPreMerge(Repository repo,
+      CodeReviewCommit commit,
+      ProjectState destProject,
+      Branch.NameKey destBranch,
+      PatchSet.Id patchSetId)
+      throws MergeValidationException;
+}

gerrit-server/src/main/java/com/google/gerrit/server/git/validators/MergeValidators.java

@@ -0,0 +1,78 @@
+// Copyright (C) 2013 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.validators;
+
+import com.google.common.collect.Lists;
+import com.google.gerrit.extensions.registration.DynamicSet;
+import com.google.gerrit.reviewdb.client.Branch;
+import com.google.gerrit.reviewdb.client.PatchSet;
+import com.google.gerrit.server.git.CodeReviewCommit;
+import com.google.gerrit.server.project.ProjectState;
+import com.google.inject.Inject;
+
+import org.eclipse.jgit.lib.Repository;
+
+import java.util.List;
+
+public class MergeValidators {
+  private final DynamicSet<MergeValidationListener> mergeValidationListeners;
+
+  public interface Factory {
+    MergeValidators create();
+  }
+
+  @Inject
+  MergeValidators(DynamicSet<MergeValidationListener> mergeValidationListeners) {
+    this.mergeValidationListeners = mergeValidationListeners;
+  }
+
+  public void validatePreMerge(Repository repo,
+      CodeReviewCommit commit,
+      ProjectState destProject,
+      Branch.NameKey destBranch,
+      PatchSet.Id patchSetId)
+      throws MergeValidationException {
+    List<MergeValidationListener> validators = Lists.newLinkedList();
+
+    validators.add(new PluginMergeValidationListener(mergeValidationListeners));
+
+    for (MergeValidationListener validator : validators) {
+      validator.onPreMerge(repo, commit, destProject, destBranch, patchSetId);
+    }
+  }
+
+  /** Execute merge validation plug-ins */
+  public static class PluginMergeValidationListener implements
+      MergeValidationListener {
+    private final DynamicSet<MergeValidationListener> mergeValidationListeners;
+
+    public PluginMergeValidationListener(
+        DynamicSet<MergeValidationListener> mergeValidationListeners) {
+      this.mergeValidationListeners = mergeValidationListeners;
+    }
+
+    @Override
+    public void onPreMerge(Repository repo,
+        CodeReviewCommit commit,
+        ProjectState destProject,
+        Branch.NameKey destBranch,
+        PatchSet.Id patchSetId)
+        throws MergeValidationException {
+      for (MergeValidationListener validator : mergeValidationListeners) {
+        validator.onPreMerge(repo, commit, destProject, destBranch, patchSetId);
+      }
+    }
+  }
+}