def diff model: nil, filter: nil
      cmd = 'git diff '
      if !model.nil? && model.downcase == 'cached'
        cmd = cmd + '--cached '
      end
      cmd = cmd + '--name-only '
      if !filter.nil?
        cmd = cmd + '--diff-filter=' + filter
      end
      `#{cmd}`.chomp.split
    end
def diff model: nil, filter: nil
      cmd = 'git diff '
      if !model.nil? && model.downcase == 'cached'
        cmd = cmd + '--cached '
      end
      cmd = cmd + '--name-only '
      if !filter.nil?
        cmd = cmd + '--diff-filter=' + filter
      end
      `#{cmd}`.chomp.split
    end
git diff {--cached} --name-only {--diff-filter=}