CodeReviewCommit: Add a static method to create a RevWalk

Several places in the code construct a new RevWalk subclass that
produces CodeReviewCommits. Consolidate these into a single method.

Change-Id: If38a648fb95d86f8f8297d1ddacfb9e62a96c8e3

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

@@ -21,12 +21,22 @@ import com.google.gerrit.server.project.ChangeControl;
 
 import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevWalk;
 
 import java.util.List;
 
 /** Extended commit entity with code review specific metadata. */
 public class CodeReviewCommit extends RevCommit {
+  public static RevWalk newRevWalk(Repository repo) {
+    return new RevWalk(repo) {
+      @Override
+      protected RevCommit createCommit(AnyObjectId id) {
+        return new CodeReviewCommit(id);
+      }
+    };
+  }
   static CodeReviewCommit error(final CommitMergeStatus s) {
     final CodeReviewCommit r = new CodeReviewCommit(ObjectId.zeroId());
     r.statusCode = s;

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

@@ -73,7 +73,6 @@ import com.google.inject.assistedinject.Assisted;
 
 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
 import org.eclipse.jgit.errors.RepositoryNotFoundException;
-import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.ObjectInserter;
@@ -389,12 +388,7 @@ public class MergeOp {
       throw new MergeException(m, err);
     }
 
-    rw = new RevWalk(repo) {
+    rw = CodeReviewCommit.newRevWalk(repo);
-      @Override
-      protected RevCommit createCommit(final AnyObjectId id) {
-        return new CodeReviewCommit(id);
-      }
-    };
     rw.sort(RevSort.TOPO);
     rw.sort(RevSort.COMMIT_TIME_DESC, true);
     canMergeFlag = rw.newFlag("CAN_MERGE");

gerrit-server/src/main/java/com/google/gerrit/server/query/change/ConflictsPredicate.java

@@ -35,7 +35,6 @@ import com.google.gwtorm.server.OrmException;
 import com.google.inject.Provider;
 
 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
-import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Ref;
@@ -112,12 +111,7 @@ class ConflictsPredicate extends OrPredicate<ChangeData> {
             Repository repo =
                 args.repoManager.openRepository(otherChange.getProject());
             try {
-              RevWalk rw = new RevWalk(repo) {
+              RevWalk rw = CodeReviewCommit.newRevWalk(repo);
-                @Override
-                protected RevCommit createCommit(AnyObjectId id) {
-                  return new CodeReviewCommit(id);
-                }
-              };
               try {
                 RevFlag canMergeFlag = rw.newFlag("CAN_MERGE");
                 CodeReviewCommit commit =