private void SnapshotTimeline_SelectionChanged(object sender, EventArgs e)
{
DiffSelection.Enabled = SnapshotTimeline.HasSelection &&
(SnapshotTimeline.Selection.First != SnapshotTimeline.Selection.Second);
ViewSelection.Enabled = SnapshotTimeline.HasSelection &&
(SnapshotTimeline.Selection.First == SnapshotTimeline.Selection.Second);
}