bug#3746: M-r in comint mode should use isearch

[Juri Linkov]

>   > > The problem with that is that C-s (and C-r) already have bindings in
>   > > comint modes, and changing them would not be liked by most users.
>   > > Doing M-r and then C-s/C-r seems a bit cumbersome.
>   > > IMHO just using M-r for incremental history search will provide no
>   > > surprises for the user, and it seems like a natural extension of the
>   > > current behavior.
>   >
>   > Currently M-r typed in the shell buffer activates the minibuffer with
>   > the prompt "Previous input matching (regexp): ".  I doubt that users
>   > will like to see Isearch activated instead of this minibuffer.
>
> Why not?  It does provide the same functionality and it seems easier to
> use.  Maybe the prompt would need to be adjusted, but, IMHO, it's
> doubtful the users would be unpleasantly surprised by the behavior...

M-r has a different UI. Its main difference that it is a non-incremental
regexp search unlike C-s that is an incremental string search.  Both bash
and the Emacs minibuffer activate Isearch on C-s, so it would be natural
to do the same in shell buffers.  We could try the same context-dependent
dwim approach used by the option of `dired-isearch-filenames', i.e.
"When point is on a file name initially, search file names".  So when point
is on the shell prompt then run Isearch on the shell history, otherwise
run Isearch on the shell buffer.

What to do with the prompt is more difficult problem.  Bash replaces the
shell prompt with the search prompt.  Perhaps we should do the same.

-- 
Juri Linkov
http://www.jurta.org/emacs/