bug#8447: Undoing M-x revert-buffer

[Drew Adams <drew.adams@oracle.com>]

> >> I just installed into the trunk a patch which should make
> >> revert-buffer undoable.
> >
> > FWIW, see my comment on this in the help list:
> > http://lists.gnu.org/archive/html/help-gnu-emacs/2013-05/msg00671.html
> >
> > In sum, why?  And why no discussion?  Where was the "bug"?

> as it happened, run sometimes into this:
> reverting the buffer, which turned out not the right thing - but undo-
> history was lost. Consider it a useful change, thanks.

By "turned out not the right thing" I guess you mean that someone used `revert-buffer' interactively and by mistake.  And by mistake also _confirmed_ reverting.  Yes, it can happen (to anyone).

So define a command `revert-buffer-keeping-undo', and use that interactively instead of `revert-buffer'.  Or define a variable (option or internal) `revert-buffer-keeps-undo'.

What you cite is a user-interface issue - i.e., only for interactive use of the command.  Such a change, to safeguard against mistaken reverting, is akin to removing files to a trash bin instead of deleting them.  But we did not just willy nilly change the behavior of the basic function (command) `delete-file' when we added support for a recycle/trash bin.  That's not the right approach.

With extra interactive protection as the only reason, this is also akin to some users (me, for instance) wanting `C-w' to prompt for confirmation if the region is over a certain size (as in wimpy-del.el).  Certainly such safeguard features can be useful.

But this change goes way beyond offering users optional extra protection.  `revert-buffer' is also used in basic code.

The right way to add such protection against mistaken reversion is to create a separate command or option, letting users choose to use it or not.  And leave the basic `revert-buffer' alone.

FWIW, I agree that such a feature can be useful for reverting interactively.

And why no discussion before making such a change?