bug#74352: 29.4; emerge-files with tramp + local file fails

bug#74352: 29.4; emerge-files with tramp + local file fails

[Jörg Sommer]

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Hi,

when running `emerge-files` with `/ssh:remote:file` and `~/local-file` I get
the buffer `*emerge-diff-errors*` with:

```
diff: /tmp/tramp.wlcRNL: No such file or directory
diff: /home/joerg/local-file: No such file or directory
```

This change solves the problem:

```diff
diff --git lisp/vc/emerge.el lisp/vc/emerge.el
index ca48f2f3c7b..562041e4232 100644
--- lisp/vc/emerge.el
+++ lisp/vc/emerge.el
@@ -581,6 +581,7 @@ emerge-make-diff-list
   (setq emerge-diff-buffer (get-buffer-create "*emerge-diff*"))
   (with-current-buffer
       emerge-diff-buffer
+    (setq default-directory (file-name-directory file-A))
     (erase-buffer)
     (shell-command
      (format "%s %s %s %s"
```

Regards Jörg

In GNU Emacs 29.4 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.42, cairo
 version 1.18.0) of 2024-06-30, modified by Debian built on sbuild
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-- 
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bug#74352: 29.4; emerge-files with tramp + local file fails

[Eli Zaretskii]

> Date: Wed, 13 Nov 2024 20:11:10 +0100
> From: Jörg Sommer <joerg@jo-so.de>
> 
> when running `emerge-files` with `/ssh:remote:file` and `~/local-file` I get
> the buffer `*emerge-diff-errors*` with:
> 
> ```
> diff: /tmp/tramp.wlcRNL: No such file or directory
> diff: /home/joerg/local-file: No such file or directory
> ```
> 
> This change solves the problem:
> 
> ```diff
> diff --git lisp/vc/emerge.el lisp/vc/emerge.el
> index ca48f2f3c7b..562041e4232 100644
> --- lisp/vc/emerge.el
> +++ lisp/vc/emerge.el
> @@ -581,6 +581,7 @@ emerge-make-diff-list
>    (setq emerge-diff-buffer (get-buffer-create "*emerge-diff*"))
>    (with-current-buffer
>        emerge-diff-buffer
> +    (setq default-directory (file-name-directory file-A))

Thanks, but why file-A?  Isn't the problem symmetric wrt the two
files?  Or what am I missing?

bug#74352: 29.4; emerge-files with tramp + local file fails

[Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Jörg Sommer <joerg@jo-so.de> writes:

> Hi,

Hi Joerg,

> when running `emerge-files` with `/ssh:remote:file` and `~/local-file` I get
> the buffer `*emerge-diff-errors*` with:
>
> ```
> diff: /tmp/tramp.wlcRNL: No such file or directory
> diff: /home/joerg/local-file: No such file or directory
> ```

Thanks for the report. There is also bug#6850 about the same topic, I've
merged both.

> This change solves the problem:
>
> ```diff
> diff --git lisp/vc/emerge.el lisp/vc/emerge.el
> index ca48f2f3c7b..562041e4232 100644
> --- lisp/vc/emerge.el
> +++ lisp/vc/emerge.el
> @@ -581,6 +581,7 @@ emerge-make-diff-list
>    (setq emerge-diff-buffer (get-buffer-create "*emerge-diff*"))
>    (with-current-buffer
>        emerge-diff-buffer
> +    (setq default-directory (file-name-directory file-A))
>      (erase-buffer)
>      (shell-command
>       (format "%s %s %s %s"
> ```

Unfortunately, nobody felt comfortable to work on this over the
years. I'll take the stab, and check your patch next days. So we should
fix this after so many years.

> Regards Jörg

Thanks for the heads-up, and best regards, Michael.

bug#74352: 29.4; emerge-files with tramp + local file fails

[Jörg Sommer]

[-- Attachment #1: Type: text/plain, Size: 1574 bytes --]

Eli Zaretskii schrieb am Do 14. Nov, 09:05 (+0200):
> > Date: Wed, 13 Nov 2024 20:11:10 +0100
> > From: Jörg Sommer <joerg@jo-so.de>
> > 
> > when running `emerge-files` with `/ssh:remote:file` and `~/local-file` I get
> > the buffer `*emerge-diff-errors*` with:
> > 
> > ```
> > diff: /tmp/tramp.wlcRNL: No such file or directory
> > diff: /home/joerg/local-file: No such file or directory
> > ```
> > 
> > This change solves the problem:
> > 
> > ```diff
> > diff --git lisp/vc/emerge.el lisp/vc/emerge.el
> > index ca48f2f3c7b..562041e4232 100644
> > --- lisp/vc/emerge.el
> > +++ lisp/vc/emerge.el
> > @@ -581,6 +581,7 @@ emerge-make-diff-list
> >    (setq emerge-diff-buffer (get-buffer-create "*emerge-diff*"))
> >    (with-current-buffer
> >        emerge-diff-buffer
> > +    (setq default-directory (file-name-directory file-A))
> 
> Thanks, but why file-A?  Isn't the problem symmetric wrt the two
> files?  Or what am I missing?

In *emerge-setup* above is this code:

```
	 ;; create the merge buffer from buffer A, so it inherits buffer A's
	 ;; default directory, etc.
	 (merge-buffer (with-current-buffer
			   buffer-A
			 (get-buffer-create merge-buffer-name))))
```

But I think it doesn't matter if A or B. The problem is that
emerge-diff-buffer has the remote directory and shell command tries to
execute the command on the remote side even through file-A and file-B were
copied to local side in *emerge-files-internal*.


Kind regards, Jörg

-- 
Die am Lautesten reden, haben stets am wenigsten zu sagen.

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bug#74352: 29.4; emerge-files with tramp + local file fails

[Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Jörg Sommer <joerg@jo-so.de> writes:

> Hi,

Hi Jörg,

> when running `emerge-files` with `/ssh:remote:file` and `~/local-file` I get
> the buffer `*emerge-diff-errors*` with:
>
> ```
> diff: /tmp/tramp.wlcRNL: No such file or directory
> diff: /home/joerg/local-file: No such file or directory
> ```

I can reproduce the problem if file-A is remote, and file-B is
local. Also, if both file-A and file-B are remote.

If both files are local, or file-A is local and file-B is remote, emerge
works as exptected.

The crucial point seems to be that file-A is a remote one.

> This change solves the problem:
>
> ```diff
> diff --git lisp/vc/emerge.el lisp/vc/emerge.el
> index ca48f2f3c7b..562041e4232 100644
> --- lisp/vc/emerge.el
> +++ lisp/vc/emerge.el
> @@ -581,6 +581,7 @@ emerge-make-diff-list
>    (setq emerge-diff-buffer (get-buffer-create "*emerge-diff*"))
>    (with-current-buffer
>        emerge-diff-buffer
> +    (setq default-directory (file-name-directory file-A))
>      (erase-buffer)
>      (shell-command
>       (format "%s %s %s %s"
> ```

The point is, that emerge calls the 'diff' program for either the file
itself (if local), or a local copy of the file (if remote). A consistent
solution is therefore to set a local default directory, like

--8<---------------cut here---------------start------------->8---
    (setq default-directory temporary-file-directory)
--8<---------------cut here---------------end--------------->8---

instead of your change. Would you like to check?

However, this won't be a complete solution. There are other places in
emerge.el, where the temporary buffer for calling 'diff' must have a
local default directory. I'm not an emerge aficionado (haven't used it
until now). Would you like to produce a complete patch, based on my
proposal above?

> Regards Jörg

Best regards, Michael.

bug#74352: 29.4; emerge-files with tramp + local file fails

[Jörg Sommer]

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Michael Albinus schrieb am Sa 16. Nov, 13:21 (+0100):
> Jörg Sommer <joerg@jo-so.de> writes:
> > This change solves the problem:
> >
> > ```diff
> > diff --git lisp/vc/emerge.el lisp/vc/emerge.el
> > index ca48f2f3c7b..562041e4232 100644
> > --- lisp/vc/emerge.el
> > +++ lisp/vc/emerge.el
> > @@ -581,6 +581,7 @@ emerge-make-diff-list
> >    (setq emerge-diff-buffer (get-buffer-create "*emerge-diff*"))
> >    (with-current-buffer
> >        emerge-diff-buffer
> > +    (setq default-directory (file-name-directory file-A))
> >      (erase-buffer)
> >      (shell-command
> >       (format "%s %s %s %s"
> > ```
> 
> The point is, that emerge calls the 'diff' program for either the file
> itself (if local), or a local copy of the file (if remote). A consistent
> solution is therefore to set a local default directory, like
> 
> --8<---------------cut here---------------start------------->8---
>     (setq default-directory temporary-file-directory)
> --8<---------------cut here---------------end--------------->8---
> 
> instead of your change. Would you like to check?

This works.

But in the context of *emerge-make-diff-list* it is not very apparent why
*temporary-file-directory* is used. Maybe a comment should say that
*emerge-files-internal* copied the files there by *file-local-copy*.

> However, this won't be a complete solution. There are other places in
> emerge.el, where the temporary buffer for calling 'diff' must have a
> local default directory.

Are you sure? I see only one usage of emerge-diff-program in emerge.el.

> I'm not an emerge aficionado

Out of curiosity: Is there a better tool?



-- 
"The future is here. It's just not widely distributed yet."
                                       (William Gibson)

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bug#74352: 29.4; emerge-files with tramp + local file fails

[Michael Albinus via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Jörg Sommer <joerg@jo-so.de> writes:

Hi Joerg,

>> The point is, that emerge calls the 'diff' program for either the file
>> itself (if local), or a local copy of the file (if remote). A consistent
>> solution is therefore to set a local default directory, like
>> 
>> --8<---------------cut here---------------start------------->8---
>>     (setq default-directory temporary-file-directory)
>> --8<---------------cut here---------------end--------------->8---
>> 
>> instead of your change. Would you like to check?
>
> This works.
>
> But in the context of *emerge-make-diff-list* it is not very apparent why
> *temporary-file-directory* is used. Maybe a comment should say that
> *emerge-files-internal* copied the files there by *file-local-copy*.

Sure, it doesn't hurt :-)

My patch is rather a proof of concept. It could be improved in all directions.

>> However, this won't be a complete solution. There are other places in
>> emerge.el, where the temporary buffer for calling 'diff' must have a
>> local default directory.
>
> Are you sure? I see only one usage of emerge-diff-program in emerge.el.

There is also emerge-diff3-program, used in emerge-make-diff3-list.

And there are also emerge-rcs-ci-program and emerge-rcs-co-program, used
at different places. But I don't know whether they need special care.

>> I'm not an emerge aficionado
>
> Out of curiosity: Is there a better tool?

ediff-files, ediff-directories and ediff-revision. Because I use them
all days, I've rebound some keys in my .emacs:

--8<---------------cut here---------------start------------->8---
(require 'dired)
(define-key dired-mode-map "=" 'ediff-files)
(define-key dired-mode-map "\M-=" 'ediff-directories)

(require 'vc)
(define-key vc-prefix-map "=" 'ediff-revision)
(setq ediff-diff-options "-a")

(add-hook 'vc-dir-mode-hook
	  (lambda () (define-key vc-dir-mode-map "=" 'ediff-revision)))
--8<---------------cut here---------------end--------------->8---

Best regards, Michael.