GNU bug report logs - #35166
27.0.50; Buffer state inconsistent after vc-retrieve-tag

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Mauro Aranda <maurooaranda <at> gmail.com>
To: bug-gnu-emacs <bug-gnu-emacs <at> gnu.org>
Subject: 27.0.50; Buffer state inconsistent after vc-retrieve-tag
Date: Fri, 5 Apr 2019 18:41:34 -0300

[Message part 1 (text/plain, inline)]

Hello.

Suppose the following workflow for exploring code, under version
control:
1. Start emacs: emacs -Q.
2. Visit a directory in Dired mode, e.g. C-x d "emacs/lisp/eshell".
3. Navigate to a file, and type 'v'.
4. While exploring, one may wish to switch branch, so type:
C-x v r BRANCH-NAME

I find the following to be inconsistent:

'vc-retrieve-tag' makes an effort to preserve the modes in the file.
So it preserves View mode.  But the file is no longer read-only.  This
way, the buffer ends up being writable, but with View mode enabled, and
I find it a little confusing.  I understand if that is to respect
'revert-buffer' design, as I infer from this message:
[1] https://lists.gnu.org/archive/html/emacs-devel/2004-09/msg00002.html
But I think the user could at least be warned about this, in the manual
(perhaps in the VC Branches section).

After reading [1], I tested the workflow with auto-revert-mode set to 't',
and
it works as expected, based on the information in the following messages
to [1].

Trying out simple solutions for myself, I answered "no" to the prompt
that VC puts: "Update any affected buffers? (yes or no)".  I wouldn't
answer no in the workflow I described, but I answered "no" just for the
sake of it.  I ended up with the buffer being updated, and again with
View mode enabled, but not with buffer-read-only set to 't'.
So I wonder, what is the effect of answering "yes" or "no"?  What does
it update, and what does it not?  I couldn't find such information in
the VC section of the manual.

Please, consider either improving what 'vc-retrieve-tag' does, regarding the
previous state of the buffer, or improving the documentation about this
behavior.  Or, if you think I'm plain wrong, please explain me the
reasons, since I would like to understand more of it.

Best regards,
Mauro.

[Message part 2 (text/html, inline)]

Message #8 received at 35166 <at> debbugs.gnu.org (full text, mbox):

From: Mauro Aranda <maurooaranda <at> gmail.com>
To: 35166 <at> debbugs.gnu.org
Subject: Re: bug#35166: 27.0.50;
 Buffer state inconsistent after vc-retrieve-tag
Date: Sat, 4 May 2019 18:16:49 -0300

[Message part 1 (text/plain, inline)]

Hello.

Any thoughts on this?

[Message part 2 (text/html, inline)]

Message #13 received at 35166 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Mauro Aranda <maurooaranda <at> gmail.com>
Cc: 35166 <at> debbugs.gnu.org
Subject: Re: bug#35166: 27.0.50; Buffer state inconsistent after
 vc-retrieve-tag
Date: Tue, 22 Jun 2021 19:30:01 +0200

Mauro Aranda <maurooaranda <at> gmail.com> writes:

> Suppose the following workflow for exploring code, under version
> control:
> 1. Start emacs: emacs -Q.
> 2. Visit a directory in Dired mode, e.g. C-x d "emacs/lisp/eshell".
> 3. Navigate to a file, and type 'v'.
> 4. While exploring, one may wish to switch branch, so type:
> C-x v r BRANCH-NAME
>
> I find the following to be inconsistent:
>
> 'vc-retrieve-tag' makes an effort to preserve the modes in the file.
> So it preserves View mode.  But the file is no longer read-only.

I can confirm that this behaviour is still present in Emacs 28.

> This way, the buffer ends up being writable, but with View mode
> enabled, and I find it a little confusing.  I understand if that is to
> respect 'revert-buffer' design, as I infer from this message: [1]
> https://lists.gnu.org/archive/html/emacs-devel/2004-09/msg00002.html

I think this was changed in:

commit 90e118abf2dcc4aca4d7a7642247fa488554351e
Author:     Luc Teirlinck <teirllm <at> auburn.edu>
AuthorDate: Fri Sep 3 22:28:10 2004 +0000

    (auto-revert-handler): Bind `buffer-read-only' locally around the call
    to `revert-buffer'.

Reversion now preserves buffer-readedness, if I understand correctly.

> Please, consider either improving what 'vc-retrieve-tag' does, regarding the
> previous state of the buffer, or improving the documentation about this
> behavior.  Or, if you think I'm plain wrong, please explain me the
> reasons, since I would like to understand more of it.

I think it would make sense for `vc-retrieve-tag' to preserve the
readedness of the buffer.  Anybody got any comments here?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #18 received at 35166 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Mauro Aranda <maurooaranda <at> gmail.com>
Cc: 35166 <at> debbugs.gnu.org
Subject: Re: bug#35166: 27.0.50; Buffer state inconsistent after
 vc-retrieve-tag
Date: Tue, 22 Jun 2021 19:40:52 +0200

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

> Reversion now preserves buffer-readedness, if I understand correctly.

Er, sorry -- not it doesn't -- only automatic autoreversion does, as
Mauro already said.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #21 received at 35166 <at> debbugs.gnu.org (full text, mbox):

From: Mauro Aranda <maurooaranda <at> gmail.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 35166 <at> debbugs.gnu.org
Subject: Re: bug#35166: 27.0.50; Buffer state inconsistent after
 vc-retrieve-tag
Date: Wed, 23 Jun 2021 12:13:28 -0300

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

> Mauro Aranda <maurooaranda <at> gmail.com> writes:
>
>> Please, consider either improving what 'vc-retrieve-tag' does, regarding the
>> previous state of the buffer, or improving the documentation about this
>> behavior.  Or, if you think I'm plain wrong, please explain me the
>> reasons, since I would like to understand more of it.
>
> I think it would make sense for `vc-retrieve-tag' to preserve the
> readedness of the buffer.  Anybody got any comments here?

FWIW, I've been saving the readedness since I reported this bug by using
before-revert-hook and after-revert-hook.

I don't know if vc-retrieve-tag should save it, but I think leaving the
buffer in this state (view-mode on and not read-only) should be avoided,
if possible.

Message #24 received at 35166 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Mauro Aranda <maurooaranda <at> gmail.com>
Cc: 35166 <at> debbugs.gnu.org
Subject: Re: bug#35166: 27.0.50; Buffer state inconsistent after
 vc-retrieve-tag
Date: Thu, 22 Jul 2021 16:25:54 +0200

Mauro Aranda <maurooaranda <at> gmail.com> writes:

> FWIW, I've been saving the readedness since I reported this bug by using
> before-revert-hook and after-revert-hook.
>
> I don't know if vc-retrieve-tag should save it, but I think leaving the
> buffer in this state (view-mode on and not read-only) should be avoided,
> if possible.

Nobody else had an opinion, so I've now made revert-buffer preserve
buffer-read-only on the trunk, and we'll see whether that messes up
anybody's work flow...

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #31 received at 35166 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Kaushal Modi <kaushal.modi <at> gmail.com>
Cc: 35166 <at> debbugs.gnu.org, Emacs developers <emacs-devel <at> gnu.org>
Subject: Re: Change in `revert-buffer' behavior [28.0.50]
Date: Tue, 27 Jul 2021 17:25:40 +0200

Kaushal Modi <kaushal.modi <at> gmail.com> writes:

> When I change the read-onlyness of a file from the disk, M-x revert-buffer
> doesn't reflect that change any more. This is really important as I am working in
> a centralized VCS where the files have to be "checked out" i.e. make writable
> before I can modify them.

I've now reverted the change and reopened bug#35166 -- the problem there
will have to be fixed in a different way.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #34 received at 35166 <at> debbugs.gnu.org (full text, mbox):

From: Kaushal Modi <kaushal.modi <at> gmail.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 35166 <at> debbugs.gnu.org, Emacs developers <emacs-devel <at> gnu.org>
Subject: Re: Change in `revert-buffer' behavior [28.0.50]
Date: Tue, 27 Jul 2021 11:39:55 -0400

[Message part 1 (text/plain, inline)]

On Tue, Jul 27, 2021 at 11:25 AM Lars Ingebrigtsen <larsi <at> gnus.org> wrote:

>
> I've now reverted the change and reopened bug#35166 -- the problem there
> will have to be fixed in a different way.
>

Thanks for that quick fix! This restores the old `revert-buffer' behavior.

[Message part 2 (text/html, inline)]

Message #39 received at 35166 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Mauro Aranda <maurooaranda <at> gmail.com>
Cc: 35166 <at> debbugs.gnu.org
Subject: Re: bug#35166: 27.0.50; Buffer state inconsistent after
 vc-retrieve-tag
Date: Wed, 24 Aug 2022 13:39:23 +0200

Mauro Aranda <maurooaranda <at> gmail.com> writes:

> Suppose the following workflow for exploring code, under version
> control:
> 1. Start emacs: emacs -Q.
> 2. Visit a directory in Dired mode, e.g. C-x d "emacs/lisp/eshell".
> 3. Navigate to a file, and type 'v'.
> 4. While exploring, one may wish to switch branch, so type:
> C-x v r BRANCH-NAME

This is now fixed in Emacs 29.

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