Re: TODO

[Richard Stallman]

    If `insert-file-contents' does not change any part of the buffer, it's
    basically a no-op.  I see hence no reason for it to flush the undo-list
    in that case.

The point is that it is somewhat unclean for the flushing to depend on
the data in the file.  So the usual ways of calling `insert-file-contents'
should either flush or not, regardless of the data in the file.