Re: [PATCH] Add facility to collect stderr of async subprocess

[Tino Calancha <tino.calancha@gmail.com>]

On Thu, 6 Oct 2016, Eli Zaretskii wrote:

>> From: Tino Calancha <tino.calancha@gmail.com>
>> Date: Thu, 6 Oct 2016 16:25:39 +0900 (JST)
>> cc: Tino Calancha <tino.calancha@gmail.com>, jwiegley@gmail.com,
>>     emacs-devel@gnu.org, michael.albinus@gmx.de
>>
>> As a bonus, several other functions will automatically inherit this
>> feature: `start-file-process', `start-process-shell-command', and
>> `start-file-process-shell-command'.
>
> As Micheal explained, start-file-process and
> start-file-process-shell-command cannot inherit this without some
> non-trivial coding for the remote case.
Fair enough, but it wouldn't be the first time that we get more
locally compared with remote, for instance:
Bug#24394
or
https://lists.gnu.org/archive/html/tramp-devel/2015-12/msg00000.html

>> Personally, i find pleasant if every function creating an asynchronous
>> process us able to separate stdout from stderr.
>
> Actually, the need in this separation is rather rare.  Which is not
> surprising, since running commands from a terminal by default delivers
> both stdout and stderr to the screen, and the cases where these are
> redirected separately are rare.
It depends of what the user is doing.  `shell-command' and 
`async-shell-command' have being offering that since long time ago.

It is quite common redirect stderr from a shell: all shells allow that 
AFAIK.
In Emacs, there is the idiom that everything is a buffer, so redirecting
stderr to a buffer instead of a file (as `call-process') seems the
natural thing.  Or maybe I'm missing something.