GetRelated: Discard single commit by its hash instead of change/ps

change/ps is only available for open changes.

Change-Id: I04e96635b01a231918f2adf83fd759376b9be80a
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/change/GetRelated.java b/gerrit-server/src/main/java/com/google/gerrit/server/change/GetRelated.java
index 4834950..077ec6f1 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/change/GetRelated.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/change/GetRelated.java
@@ -127,9 +127,7 @@
 
     if (list.size() == 1) {
       ChangeAndCommit r = list.get(0);
-      if (r._changeNumber != null && r._revisionNumber != null
-          && r._changeNumber == rsrc.getChange().getChangeId()
-          && r._revisionNumber == rsrc.getPatchSet().getPatchSetId()) {
+      if (r.commit != null && r.commit.commit.equals(rsrc.getPatchSet().getRevision().get())) {
         return Collections.emptyList();
       }
     }