GitUI.FormFileHistory.OpenWithDifftoolToolStripMenuItemClick C# (CSharp) Метод

        private void OpenWithDifftoolToolStripMenuItemClick(object sender, EventArgs e)
        {
            var selectedRows = FileChanges.GetRevisions();
            string rev1;
            string rev2;
            switch (selectedRows.Count)
            {
                case 1:
                    {
                        rev1 = selectedRows[0].Guid;
                        var parentGuids = selectedRows[0].ParentGuids;
                        if (parentGuids != null && parentGuids.Length > 0)
                        {
                            rev2 = parentGuids[0];
                        }
                        else
                        {
                            rev2 = rev1;
                        }
                    }
                    break;
                case 0:
                    return;
                default:
                    rev1 = selectedRows[0].Guid;
                    rev2 = selectedRows[1].Guid;
                    break;
            }

            var output = GitCommands.GitCommands.OpenWithDifftool(FileName, rev1, rev2);
            if (!string.IsNullOrEmpty(output))
                MessageBox.Show(output);
        }