Merge "Add explanation of dummy approvals to ApprovalsUtil"

gerrit-server/src/main/java/com/google/gerrit/server/ApprovalsUtil.java

@@ -34,6 +34,16 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 
+/**
+ * Utility functions to manipulate patchset approvals.
+ * <p>
+ * Approvals are overloaded, they represent both approvals and reviewers
+ * which should be CCed on a change.  To ensure that reviewers are not lost
+ * there must always be an approval on each patchset for each reviewer,
+ * even if the reviewer hasn't actually given a score to the change.  To
+ * mark the "no score" case, a dummy approval, which may live in any of
+ * the available categories, with a score of 0 is used.
+ */
 public class ApprovalsUtil {
   private final ReviewDb db;
   private final ApprovalTypes approvalTypes;