protected HgDiffFragment(HgDiffFragmentType type, string content, int indexA, int indexB)
 {
     Type = type;
     Content = content;
     IndexA = indexA;
     IndexB = indexB;
 }
        //public IList<HgDiffInlineFragment> Diff { get; set; } 

        public HgDiffLineFragment(HgDiffFragmentType type, string content, int index, int indexA, int indexB) : base(type, content, indexA, indexB)
        {
            Index = index;
        }
 public HgDiffInlineFragment(HgDiffFragmentType type, string content, int indexA, int indexB) : 
     base(type, content, indexA, indexB)
 {
 }