suggestion (comint-kill-output): prefix arg to remove all old output

[Michael John Downes]

In GNU Emacs 20.7.1 (sparc-sun-solaris2.7, X toolkit)
 of Thu Sep 21 2000 on thor
configured using `configure  --with-x'

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

I suggest that it would be useful for the comint-kill-output command in
a *shell* buffer to interpret a C-u prefix argument as meaning "kill the
output of all the preceding shell commands, not just the most recent
one".

It is not terribly difficult to get the desired effect "by hand", e.g.
when the cursor is at the latest shell prompt C-a M-< C-w C-e, but where
the lack of the suggested feature costs users (if my experience is any
indication) is in the amount of time spent trying to figure out by
searching the documentation if such a feature is available, and if so
whether it is bound to any key. If it were a documented variant of
comint-kill-output, I would have found it rather quickly.

I checked also in Emacs 21.1 and the situation seems to be still the
same there, although the name comint-kill-output has been superseded by
comint-delete-output.

Recent input:
... f8 r e p o r return

Recent messages:
Loading /usr/local/libexec/emacs/20.7/sparc-sun-solaris2.7/fns-20.7.1.el 
(source)...
Loading /usr/local/libexec/emacs/20.7/sparc-sun-solaris2.7/fns-20.7.1.el 
(source)...done
Loading find-func...
Loading find-func...done
Note: file is write protected
Fontifying comint.el...
Fontifying comint.el... (regexps.............)
Note: file is write protected
Loading emacsbug...
Loading emacsbug...done