Add realAuthor to ChangeMessageInfo

Currently, change messages posted on behalf of another user lead to
confusion when they are displayed in the UI. One example is that the CI
removes a user's vote on behalf of them. This makes it look like they
removed it themselves which is not intended.

The new realAuthor field will let the UI display this in a more
understandable way for the user.

Change-Id: I9080ae3ed7aaa9b61501c093cee3dd7f02768d49

Documentation/rest-api-changes.txt

@@ -5300,6 +5300,10 @@ attached to a change.
 Author of the message as an
 link:rest-api-accounts.html#account-info[AccountInfo] entity. +
 Unset if written by the Gerrit system.
+|`real_author`         |optional|
+Real author of the message as an
+link:rest-api-accounts.html#account-info[AccountInfo] entity. +
+Set if the message was posted on behalf of another user.
 |`date`            ||
 The link:rest-api.html#timestamp[timestamp] this message was posted.
 |`message`            ||The text left by the user.

gerrit-acceptance-tests/src/test/java/com/google/gerrit/acceptance/rest/account/ImpersonationIT.java

@@ -39,8 +39,10 @@ import com.google.gerrit.extensions.api.changes.ReviewInput.RobotCommentInput;
 import com.google.gerrit.extensions.api.changes.RevisionApi;
 import com.google.gerrit.extensions.api.changes.SubmitInput;
 import com.google.gerrit.extensions.api.groups.GroupInput;
+import com.google.gerrit.extensions.client.ListChangesOption;
 import com.google.gerrit.extensions.client.Side;
 import com.google.gerrit.extensions.common.AccountInfo;
+import com.google.gerrit.extensions.common.ChangeInfo;
 import com.google.gerrit.extensions.common.ChangeMessageInfo;
 import com.google.gerrit.extensions.common.CommentInfo;
 import com.google.gerrit.extensions.common.GroupInfo;
@@ -62,6 +64,7 @@ import com.google.gerrit.server.git.ProjectConfig;
 import com.google.gerrit.server.project.Util;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.inject.Inject;
+import java.util.EnumSet;
 import org.apache.http.Header;
 import org.apache.http.message.BasicHeader;
 import org.junit.After;
@@ -529,6 +532,28 @@ public class ImpersonationIT extends AbstractDaemonTest {
     assertThat(m.getRealAuthor()).isEqualTo(admin.id); // not user2
   }
 
+  @Test
+  public void changeMessageCreatedOnBehalfOfHasRealUser() throws Exception {
+    allowCodeReviewOnBehalfOf();
+
+    PushOneCommit.Result r = createChange();
+    ReviewInput in = new ReviewInput();
+    in.onBehalfOf = user.id.toString();
+    in.message = "Message on behalf of";
+    in.label("Code-Review", 1);
+
+    setApiUser(accounts.user2());
+    gApi.changes().id(r.getChangeId()).revision(r.getPatchSetId().getId()).review(in);
+
+    ChangeInfo info =
+        gApi.changes().id(r.getChangeId()).get(EnumSet.of(ListChangesOption.MESSAGES));
+    assertThat(info.messages).hasSize(2);
+
+    ChangeMessageInfo changeMessageInfo = Iterables.getLast(info.messages);
+    assertThat(changeMessageInfo.realAuthor).isNotNull();
+    assertThat(changeMessageInfo.realAuthor._accountId).isEqualTo(accounts.user2().id.get());
+  }
+
   private void allowCodeReviewOnBehalfOf() throws Exception {
     ProjectConfig cfg = projectCache.checkedGet(project).getConfig();
     LabelType codeReviewType = Util.codeReview();

gerrit-extension-api/src/main/java/com/google/gerrit/extensions/common/ChangeMessageInfo.java

@@ -20,6 +20,7 @@ public class ChangeMessageInfo {
   public String id;
   public String tag;
   public AccountInfo author;
+  public AccountInfo realAuthor;
   public Timestamp date;
   public String message;
   public Integer _revisionNumber;

gerrit-server/src/main/java/com/google/gerrit/server/change/ChangeJson.java

@@ -1030,6 +1030,10 @@ public class ChangeJson {
         cmi.message = message.getMessage();
         cmi.tag = message.getTag();
         cmi._revisionNumber = patchNum != null ? patchNum.get() : null;
+        Account.Id realAuthor = message.getRealAuthor();
+        if (realAuthor != null) {
+          cmi.realAuthor = accountLoader.get(realAuthor);
+        }
         result.add(cmi);
       }
     }