bug#42922: 27.1; shell-command-dont-erase-buffer not honored when the existing shell buffer is remote

bug#42922: 27.1; shell-command-dont-erase-buffer not honored when the existing shell buffer is remote

[Sean McAfee]

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Starting from emacs -Q:

Set the variable shell-command-dont-erase-buffer to a true value, say
end-last-out.

Run an asynchronous shell command: M-& echo foo RET

The buffer *Async Shell Command* appears, showing the word "foo".

Run another async command: M-& echo bar RET

The word "bar" is appended on a new line in the existing async shell
command buffer, as expected.

Change to that buffer, and cd to any remote directory:
M-x cd RET /ssh:remote: RET

Run another async command, to be executed in the remote directory:
M-& echo baz RET

Now the word "baz" entirely replaces the contents of the buffer, instead
of being appended on a new line.



In GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
 of 2020-08-18 built on SeanMc
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
System Description: Ubuntu 18.04.5 LTS

Recent messages:
Loading /home/mcafee/.emacs-custom.el (source)...done
Waiting for git... [2 times]
Iedit default key binding is C-;
Loading /home/mcafee/emacs/laptop.el (source)...done
Package cl is deprecated
Warning: desktop file appears to be in use by PID 15481.
Using it may cause conflicts.  Use it anyway? (y or n) n
Desktop file in use; not loaded.
Turning on magit-auto-revert-mode...done
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured features:
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ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF XFT ZLIB
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Important settings:
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  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
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Load-path shadows:
~/emacs/ack hides /home/mcafee/.emacs.d/elpa/ack-1.10/ack
~/emacs/chinese hides /home/mcafee/emacs-27.1/lisp/language/chinese
~/emacs/japanese hides /home/mcafee/emacs-27.1/lisp/language/japanese
/home/mcafee/.emacs.d/elpa/seq-20151121.1017/seq hides
/home/mcafee/emacs-27.1/lisp/emacs-lisp/seq

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Memory information:
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bug#42922: 27.1; shell-command-dont-erase-buffer not honored when the existing shell buffer is remote

[Michael Albinus]

Sean McAfee <eefacm@gmail.com> writes:

Hi Sean,

> Starting from emacs -Q:
>
> Set the variable shell-command-dont-erase-buffer to a true value, say
> end-last-out.
>
> Run an asynchronous shell command: M-& echo foo RET
>
> The buffer *Async Shell Command* appears, showing the word "foo".
>
> Run another async command: M-& echo bar RET
>
> The word "bar" is appended on a new line in the existing async shell
> command buffer, as expected.
>
> Change to that buffer, and cd to any remote directory:
> M-x cd RET /ssh:remote: RET
>
> Run another async command, to be executed in the remote directory:
> M-& echo baz RET
>
> Now the word "baz" entirely replaces the contents of the buffer,
> instead
> of being appended on a new line.

This is bug#39067.

> In GNU Emacs 27.1 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.30)
>  of 2020-08-18 built on SeanMc
> Windowing system distributor 'The X.Org Foundation', version
> 11.0.11906000
> System Description: Ubuntu 18.04.5 LTS

The fix didn't find its way into Emacs 27.1, because it happened when
Emacs 27.1 was already in pretest. The fix is contained in Emacs' master
branch (aka Emacs 28.0.50), and in Tramp 2.4.4.1 of GNU ELPA, which you
can install.

It will be merged into the emacs-27 branch, Emacs 27.2 will contain the fix.

Best regards, Michael.