Setting only clone puts amoeba in indiscriminate mode

[benjamin-hull]

This is a sub-issue or related to #75. If you have a clone declaration but set neither include or exclude on a model, amoeba is set to indiscriminate/copy everything mode, as both amoeba.includes and amoeba.excludes is empty.

A fix which I'm using ensures the cloned column is also present in the includes in this case. Seems to work for my use case:

def apply_clones
  amoeba.clones.each do |clone_field|
    ensure_clone_in_includes(clone_field)
    exclude_clone_if_has_many_through(clone_field)
  end
end

# If the field to be cloned isn't in the includes, add it so it 
# can be processed in the apply_associations step.
# This handles the case where no includes or excludes are set.
def ensure_clone_in_includes(clone_field)
  return if amoeba.excludes.present?
  amoeba.includes[clone_field] = {} unless amoeba.includes.values.include?(clone_field)
end

Happy to place a PR with this change if someone wouldn't mind reviewing it.