message: Log files joined in IndexFile merges.
diff: @@ -1188,7 +1188,11 @@ bool IndexMergeIndexUpdates(QueueManager* queue) {
  did_merge = true;
  Timer time;
  root->update.Merge(to_join->update);
  - time.ResetAndPrint("Joining two querydb updates");
  + time.ResetAndPrint("Joined querydb updates for files: " +
  + StringJoinMap(root->update.files_def_update,
  + [](const QueryFile::DefUpdate& update) {
  + return update.path;
  + }));
  }
  }
  