Fix rendering of change edits in change and diff screens

During recent refactoring in I2d961f8d and I7ef198dd rendering of
change edits in change and diff screens was broken. Two REST handlers
return 404 now:

* GET /changes/<change-id>/revisions/<revision-id>/files
* GET /changes/<change-id>/revisions/<revision-id>/files/<name>/diff

Rectify it by restoring the removed code.

Test Plan:

* Upload change or create change edit online
* Modify one existing or add new file
* Save changes in editor
* Reload the change
* Open the modified file in diff screen

Change-Id: I8ac1b811d3385ce8c21f563cfa1b30fe81467ea0

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

@@ -120,6 +120,10 @@ public class Revisions implements ChildCollection<ChangeResource, RevisionResour
           out.add(new RevisionResource(change, ps));
         }
       }
+      // Not an existing patch set on a change, but might be an edit.
+      if (out.isEmpty() && id.length() == RevId.LEN) {
+        return loadEdit(change, new RevId(id));
+      }
       return out;
     }
   }

gerrit-server/src/main/java/com/google/gerrit/server/patch/PatchScriptFactory.java

@@ -159,7 +159,9 @@ public class PatchScriptFactory implements Callable<PatchScript> {
 
     PatchSet psEntityA = psa != null
         ? psUtil.get(db, control.getNotes(), psa) : null;
-    PatchSet psEntityB = psUtil.get(db, control.getNotes(), psb);
+    PatchSet psEntityB = psb.get() == 0
+        ? new PatchSet(psb)
+        : psUtil.get(db, control.getNotes(), psb);
 
     aId = psEntityA != null ? toObjectId(psEntityA) : null;
     bId = toObjectId(psEntityB);
@@ -218,13 +220,12 @@ public class PatchScriptFactory implements Callable<PatchScript> {
 
   private ObjectId toObjectId(PatchSet ps) throws NoSuchChangeException,
       AuthException, NoSuchChangeException, IOException {
-    if (ps == null || ps.getRevision() == null
-        || ps.getRevision().get() == null) {
-      throw new NoSuchChangeException(changeId);
-    }
     if (ps.getId().get() == 0) {
       return getEditRev();
     }
+    if (ps.getRevision() == null || ps.getRevision().get() == null) {
+      throw new NoSuchChangeException(changeId);
+    }
 
     try {
       return ObjectId.fromString(ps.getRevision().get());