Merge branch 'stable-3.4' into stable-3.5

* stable-3.4:
  Replicate first commit tree objects

Change-Id: I4811ee73b79ae725e93af7113782781c5c6ee315

src/main/java/com/googlesource/gerrit/plugins/replication/pull/RevisionReader.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/pull/RevisionReader.java b/src/main/java/com/googlesource/gerrit/plugins/replication/pull/RevisionReader.java
index 3f03ed6..f9882e8 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/pull/RevisionReader.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/pull/RevisionReader.java
@@ -141,6 +141,7 @@
           blobs = readBlobs(project, refName, git, totalRefSize, diffEntries);
         } else {
           walk.setRecursive(true);
+          walk.setPostOrderTraversal(true);
           walk.addTree(tree);
           blobs = readBlobs(project, refName, git, totalRefSize, walk);
         }

src/test/java/com/googlesource/gerrit/plugins/replication/pull/RevisionReaderIT.java

diff --git a/src/test/java/com/googlesource/gerrit/plugins/replication/pull/RevisionReaderIT.java b/src/test/java/com/googlesource/gerrit/plugins/replication/pull/RevisionReaderIT.java
index fcd9b19..a541d7e 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/replication/pull/RevisionReaderIT.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/replication/pull/RevisionReaderIT.java
@@ -27,6 +27,7 @@
 import com.google.gerrit.entities.Change;
 import com.google.gerrit.entities.Change.Id;
 import com.google.gerrit.entities.Patch;
+import com.google.gerrit.entities.Project;
 import com.google.gerrit.entities.RefNames;
 import com.google.gerrit.extensions.api.changes.ReviewInput;
 import com.google.gerrit.extensions.api.changes.ReviewInput.CommentInput;
@@ -43,6 +44,9 @@
 import java.io.IOException;
 import java.util.List;
 import java.util.Optional;
+import java.util.stream.Collectors;
+import org.eclipse.jgit.internal.storage.dfs.InMemoryRepository;
+import org.eclipse.jgit.junit.TestRepository;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Ref;
@@ -89,6 +93,54 @@
   }
 
   @Test
+  public void shouldReadForcePushCommitWithoutParent() throws Exception {
+    String refName = "refs/heads/master";
+    Project.NameKey emptyProjectName =
+        createProjectOverAPI("emptyProject", project, false, /* submitType= */ null);
+    TestRepository<InMemoryRepository> emptyRepo = cloneProject(emptyProjectName);
+    PushOneCommit push =
+        pushFactory.create(
+            admin.newIdent(),
+            emptyRepo,
+            "subject1",
+            ImmutableMap.of("a/fileA.txt", "content 1", "b/fileB.txt", "content 2"));
+    push.setForce(true);
+    Result pushResult = push.to(refName);
+    pushResult.assertOkStatus();
+
+    try (Repository repo = repoManager.openRepository(emptyProjectName)) {
+      Optional<RevisionData> revisionDataOption =
+          Optional.ofNullable(repo.exactRef(refName))
+              .map(Ref::getObjectId)
+              .flatMap(
+                  objId -> readRevisionFromObjectUnderTest(emptyProjectName, refName, objId, 0));
+
+      assertThat(revisionDataOption.isPresent()).isTrue();
+      RevisionData revisionData = revisionDataOption.get();
+      assertThat(revisionData.getCommitObject()).isNotNull();
+      assertThat(revisionData.getCommitObject().getType()).isEqualTo(Constants.OBJ_COMMIT);
+      assertThat(revisionData.getCommitObject().getContent()).isNotEmpty();
+
+      assertThat(revisionData.getTreeObject()).isNotNull();
+      assertThat(revisionData.getTreeObject().getType()).isEqualTo(Constants.OBJ_TREE);
+      assertThat(revisionData.getTreeObject().getContent()).isNotEmpty();
+
+      assertThat(revisionData.getBlobs()).hasSize(4);
+
+      assertThat(
+              revisionData.getBlobs().stream()
+                  .filter(b -> b.getType() == Constants.OBJ_TREE)
+                  .collect(Collectors.toList()))
+          .hasSize(2);
+      assertThat(
+              revisionData.getBlobs().stream()
+                  .filter(b -> b.getType() == Constants.OBJ_BLOB)
+                  .collect(Collectors.toList()))
+          .hasSize(2);
+    }
+  }
+
+  @Test
   public void shouldReadRefMetaObjectWithMaxNumberOfParents() throws Exception {
     int numberOfParents = 3;
     setReplicationConfig(numberOfParents);
@@ -145,6 +197,11 @@
 
   private Optional<RevisionData> readRevisionFromObjectUnderTest(
       String refName, ObjectId objId, int maxParentsDepth) {
+    return readRevisionFromObjectUnderTest(project, refName, objId, maxParentsDepth);
+  }
+
+  private Optional<RevisionData> readRevisionFromObjectUnderTest(
+      Project.NameKey project, String refName, ObjectId objId, int maxParentsDepth) {
     try {
       return objectUnderTest.read(project, objId, refName, maxParentsDepth);
     } catch (Exception e) {