Re: [rant] Should reverting a buffer really discard undo history?

[Richard Stallman]

      1.  C-x C-f foo RET original contents C-x C-s

      2.  M-! echo new contents > foo RET

      3.  Try to change the buffer.

      4.  Answer `r' to the question about really editing the buffer.

      5.  Note that at this point you cannot retrieve the original buffer
          contents by undoing.

In theory, we could treat the revert operation as an undoable change
to the buffer contents.  In practice, for large buffers, that change
would be so large that it would soon be discarded from the undo list.

For even larger buffers, the result of saving the whole buffer as
an undo record would be an immediate error.  It would be impossible to
revert.

So I am against this change--at least if it were the default.