MergeOp: Record the change set

We want to record a unique identifier which can be queried later to
obtain all changes which were submitted together.

Change-Id: I5ba29aa52c5dc20b37f3b7965a026fd6e84b814b
Signed-off-by: Stefan Beller <sbeller@google.com>

gerrit-reviewdb/src/main/java/com/google/gerrit/reviewdb/client/Change.java

@@ -453,6 +453,13 @@ public final class Change {
   @Column(id = 17, notNull = false)
   protected String originalSubject;
 
+  /**
+   * Unique id for the changes submitted together assigned during merging.
+   * Only set if the status is MERGED.
+   */
+  @Column(id = 18, notNull = false)
+  protected String submissionId;
+
   protected Change() {
   }
 
@@ -479,6 +486,7 @@ public final class Change {
     currentPatchSetId = other.currentPatchSetId;
     subject = other.subject;
     originalSubject = other.originalSubject;
+    submissionId = other.submissionId;
     topic = other.topic;
   }
 
@@ -562,6 +570,14 @@ public final class Change {
     }
   }
 
+  public String getSubmissionId() {
+    return submissionId;
+  }
+
+  public void setSubmissionId(String id) {
+    this.submissionId = id;
+  }
+
   public Status getStatus() {
     return Status.forCode(status);
   }