bug#5639: 23.1.92; Undo doesn't work

[Glenn Morris]

Torsten Bronger wrote:

> If I visit the *scratch* buffer, enter a character, and use C-x u, the
> whole buffer ist emptied and the error message "Error: No further undo
> information" appears.

I cannot reproduce this, unless I press C-x u twice, in which case
emptying the whole buffer is the expected behaviour. (The insertion of
the initial scratch buffer text has been undoable in this way since
Emacs 22.1.)

> Similarly, undoing undo doesn't work anymore by using undo, hitting
> e.g. a cursor key and using undo again (for undoing the first undo).

I cannot reproduce this at all (with `emacs -Q').

> In GNU Emacs 23.1.92.2 (x86_64-unknown-linux-gnu)
>  of 2010-02-23 on wilson