Adapt to jgit 2d8777536 (servlet-4 branch)

Change-Id: Icd3dfde3aeaaf3fd8c6959681f6bb18296d79825

src/main/java/com/googlesource/gerrit/plugins/gitiles/FilteredRepository.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/gitiles/FilteredRepository.java b/src/main/java/com/googlesource/gerrit/plugins/gitiles/FilteredRepository.java
index 1ff6af0..b5843ab 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/gitiles/FilteredRepository.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/gitiles/FilteredRepository.java
@@ -36,6 +36,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import org.eclipse.jgit.annotations.NonNull;
 import org.eclipse.jgit.attributes.AttributesNodeProvider;
 import org.eclipse.jgit.lib.ObjectDatabase;
 import org.eclipse.jgit.lib.Ref;
@@ -244,6 +245,12 @@
     }
 
     @Override
+    @NonNull
+    public ReflogReader getReflogReader(@NonNull Ref ref) throws IOException {
+      return git.getReflogReader(ref);
+    }
+
+    @Override
     public List<Ref> getAdditionalRefs() throws IOException {
       return ImmutableList.copyOf(git.getRefDatabase().getAdditionalRefs());
     }