bug#10308: 24.0.92; regression: *Help* ruined for toggling read-only

[Drew Adams]

In all Emacs releases prior to Emacs 24 (and even in 24 up until the
middle of 2011), you could toggle buffer `*Help*' and edit text there
relatively normally.  Only a very few of the ordinary keyboard keys,
such as `RET', had any special meaning.  In particular, typically
self-inserting keys inserted, and deleting keys deleted.
 
Turning off read-only in *Help* has long been useful for composing
and testing *Help* displays (e.g. doc strings).  I, and I know
others as well, have used this feature for decades.  This
regression removes it.

Now, the typically self-inserting keys do nothing - no message, nada.
`C-h k' for a typical key such as `f' says it is undefined.  Why?
What good is that?  Isn't it enough that *Help* is by default
read-only?  Why fiddle with the key bindings like that?

And `DEL' (Backspace) gives the ridiculous error message `Beginning
of buffer' (huh?), no matter where point is when you hit it.  Yet
`C-d', `M-d', etc. still delete text normally.  And `M-q' still
works (thank goodness).

And `q' quits, and `z' kills the buffer , even when the buffer has
been toggled to writable!  This is crazy.  The help-mode keys
should have no such effects when the buffer is made writable.  Try
Emacs 23, to see the difference - when read-only, `q' quits; when
writable, it self-inserts - useful.

What is the point in a user making the buffer writable now?  What
can you do with it writable that you could not do with it read-only?
In effect, we've lost a useful writable help mode, since it is now
nearly the same as read-only *Help* (only a few keys such as `C-d'
are exceptionally still usable to edit).

Now, to be able to edit *Help* you need to change its mode, instead
of just hitting `C-x C-q'.  And if you are iteratively fine-tuning
doc for *Help*, then each time you refresh it from developing code,
you need to change the mode again before you can edit it.

Please revert this regression.  It is inconsistent (e.g. `DEL' vs
`C-d'), makes Emacs less useful, and serves no constructive purpose
(AFAICT - what can you do with a writable *Help* now?).  It is an
incompatible change affecting users, yet it is not even mentioned
in the NEWS.  AFAIK, it was not proposed for discussion on
emacs-devel either.

*Help* is not just a passive output message - it is a useful Emacs 
buffer.  And part of that use is editing its content.  This is
Emacs.  Let's not put obstacles in the way of users trying to
interact with the most flexible, self-documenting, customizable
editor.  If intentional, this change is misguided.
 

In GNU Emacs 24.0.92.1 (i386-mingw-nt5.1.2600) of 2011-12-06 on MARVIN
 Windowing system distributor `Microsoft Corp.', version 5.1.2600
 configured using `configure --with-gcc (4.6) --no-opt --cflags
 -ID:/devel/emacs/libs/libXpm-3.5.8/include
 -ID:/devel/emacs/libs/libXpm-3.5.8/src
 -ID:/devel/emacs/libs/libpng-dev_1.4.3-1/include
 -ID:/devel/emacs/libs/zlib-dev_1.2.5-2/include
 -ID:/devel/emacs/libs/giflib-4.1.4-1/include
 -ID:/devel/emacs/libs/jpeg-6b-4/include
 -ID:/devel/emacs/libs/tiff-3.8.2-1/include
 -ID:/devel/emacs/libs/gnutls-2.10.1/include --ldflags
 -LD:/devel/emacs/libs/gnutls-2.10.1/lib'