Adapt to change in Gerrit core

Change Iebb1a5a8d in Gerrit core changed the way how AutoMerge is
invoked. Adapt the plugin code to this.

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: I0658d17e348bb2aec56c6826184ec4afdd77e034

java/com/google/gerrit/plugins/codeowners/backend/ChangedFiles.java

diff --git a/java/com/google/gerrit/plugins/codeowners/backend/ChangedFiles.java b/java/com/google/gerrit/plugins/codeowners/backend/ChangedFiles.java
index c19358c..f03d337 100644
--- a/java/com/google/gerrit/plugins/codeowners/backend/ChangedFiles.java
+++ b/java/com/google/gerrit/plugins/codeowners/backend/ChangedFiles.java
@@ -43,7 +43,6 @@
 import org.eclipse.jgit.diff.RawTextComparator;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.ObjectId;
-import org.eclipse.jgit.lib.ObjectInserter;
 import org.eclipse.jgit.lib.ObjectReader;
 import org.eclipse.jgit.lib.Repository;
 import org.eclipse.jgit.merge.ThreeWayMergeStrategy;
@@ -167,12 +166,12 @@
       throws IOException {
     try (Timer0.Context ctx = codeOwnerMetrics.getAutoMerge.start();
         Repository repository = repoManager.openRepository(project);
-        ObjectInserter inserter = new InMemoryInserter(repository);
+        InMemoryInserter inserter = new InMemoryInserter(repository);
         ObjectReader reader = inserter.newReader();
         RevWalk revWalk = new RevWalk(reader)) {
       return autoMergerProvider
           .get()
-          .merge(repository, revWalk, inserter, mergeCommit, mergeStrategy);
+          .lookupFromGitOrMergeInMemory(repository, revWalk, inserter, mergeCommit, mergeStrategy);
     }
   }