message: Add check if leaf can be safely merged
diff: @@ -2874,7 +2874,8 @@ void TreeUnwrapper::ReshapeTokenPartitions(
  // RHS may have been further partitioned, e.g. a macro call.
  auto& children = partition.Children();
  if (children.size() == 2 &&
  - verible::is_leaf(children.front()) /* left side */) {
  + verible::is_leaf(children.front()) /* left side */ &&
  + !PartitionIsForcedIntoNewLine(children.back())) {
  verible::MergeLeafIntoNextLeaf(&children.front());
  VLOG(4) << "after merge leaf (left-into-right):\n" << partition;
  }
  