🚀 go-pugleaf

>From LAWS@SRI-AI Thu Feb  4 23:10:53 1982
The VI undo will undo any destructive command, including reads from files.
It will not undo a write to a file.  Motion commands, including searches,
are exempted so that you can examine the file before deciding to undo.

An undo may also be undone, so that you may toggle between two states.
Deleted text is shifted down through a numbered series of buffers so that
you can recover more ancient text, although this capability is a little
difficult to use.

I have been exceedingly happy with this system, and have never felt the
need for a more powerful one.  Keeping multiple versions of a file around
(even at the operating system level) quickly becomes counterproductive.
I do write a backup copy every now and then, but that's mostly for
protection against crashes.

[To be fair, VI's undo does have an implementation bug:  enormous files
cannot be handled because of "insufficient undo space."  The user is
forced to use EX, VI's siamese twin line editor.  This has no bearing
on your question, however.]

					-- Ken Laws
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