bug#14238: [PATCH] Help page for character description forgets the character

[Stefan Monnier]

> On 24.3, emacs -Q
> Type the letters AB, then put point on A. Do describe-char, then put point
> on B, and do describe-char again.
> Change the A to C, the press [back] in *Help*.
> The help page is now for C, not for A. It should be for A; you never did 
> describe-char on C.

Not sure if it is really a bug: while the name is "describe-char" what
it does is more like "describe-pos" (and indeed it receives a position
rather than a char as argument).

So when you "back" you ask to redisplay the info about the pos where
A used to be (and where C is now instead).

The data stored with `help-setup-xref' is also used for `revert-buffer'
which lets you refresh the description after the buffer was modified.


        Stefan