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

[Drew Adams]

    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.

So, it could still be considered as an option? The values of the option
would reflect a performance-vs-safety/security tradeoff. The default value
would choose performance, and the doc could tell users how to opt for more
safety/security at the price of a possible performance hit.

I'm not real familiar with the mechanics of the undo list, but couldn't the
previous file contents be stored only on disk, as a temporary file, and the
value in the undo list be just a pointer to that file instead of the file
contents?