bug#52242: 29.0.50; Feature Request: Offer to run`diff-buffer-with-file' in `recover-this-file' prompt

bug#52242: 29.0.50; Feature Request: Offer to run`diff-buffer-with-file' in `recover-this-file' prompt

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

`recover-this-file' quite helpfully shows the time of creation of the
auto-save file.  However, this is not always enough to decide whether I
should recover from said auto-save file since there's no way of knowing
if the changes in auto-save file are desirable [1] so I end up answering
yes, then run `diff-buffer-with-file' anyway.  I think having a
`diff-buffer-with-file' option like `save-some-buffers' would be a
quality-of-life improvement.

Thanks.
[1] I fat finger my keyboard quite a lot and end up garbling the file
even after explicitly saving the buffer.  When I open the file in a new
Emacs session again, I get suggested to `recover-this-file' and 8/10
times, I have to undo.  Having a diff option directly in the prompt
would save some keystrokes.

In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.27, cairo version 1.16.0)
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bug#52242: 29.0.50; Feature Request: Offer to run`diff-buffer-with-file' in `recover-this-file' prompt

[Visuwesh]

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[வியாழன் டிசம்பர் 02, 2021] Visuwesh wrote:

> `recover-this-file' quite helpfully shows the time of creation of the
> auto-save file.  However, this is not always enough to decide whether I
> should recover from said auto-save file since there's no way of knowing
> if the changes in auto-save file are desirable [1] so I end up answering
> yes, then run `diff-buffer-with-file' anyway.  I think having a
> `diff-buffer-with-file' option like `save-some-buffers' would be a
> quality-of-life improvement.

Please find attached path that uses read-answer to present the diff.


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From d64f8a1307ab82216b5f97982494945547810f64 Mon Sep 17 00:00:00 2001
From: Visuwesh <visuweshm@gmail.com>
Date: Wed, 6 Dec 2023 13:45:03 +0530
Subject: [PATCH] Offer to show diff against auto-save in recover-file

* lisp/files.el (recover-file): Show diff against the selected auto
save file.  bug#52242

* etc/NEWS: Announce the new feature.
---
 etc/NEWS      |  4 ++++
 lisp/files.el | 10 +++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/etc/NEWS b/etc/NEWS
index 29f4e5c0b66..6c2a584c355 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -258,6 +258,10 @@ called in the '--eval' expression, which is useful when those
 arguments contain arbitrary characters that otherwise might require
 elaborate and error-prone escaping (to protect them from the shell).
 
+** 'recover-this-file' can show diff between auto save file and current file.
+When answering the prompt with "diff" or "=", it now shows the diff
+between the auto save file and the current file.
+
 \f
 * Editing Changes in Emacs 30.1
 
diff --git a/lisp/files.el b/lisp/files.el
index 1cdcec23b11..d70524e4775 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -7083,7 +7083,15 @@ recover-file
 	    #'(lambda (window _value)
 		(with-selected-window window
 		  (unwind-protect
-		      (yes-or-no-p (format "Recover auto save file %s? " file-name))
+                      (let ((prompt (format "Recover auto save file %s? " file-name))
+                            (choices
+                             '(("yes" ?y "recover auto save file")
+                               ("no" ?n "don't recover auto save file")
+                               ("diff" ?= "diff auto save file with current file")))
+                            ans)
+                        (while (equal "diff" (setq ans (read-answer prompt choices)))
+                          (diff file file-name))
+                        (equal ans "yes"))
 		    (when (window-live-p window)
 		      (quit-restore-window window 'kill)))))
 	    (with-current-buffer standard-output
-- 
2.42.0

bug#52242: 29.0.50; Feature Request: Offer to run`diff-buffer-with-file' in `recover-this-file' prompt

[Visuwesh]

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[புதன் டிசம்பர் 06, 2023] Visuwesh wrote:

> [வியாழன் டிசம்பர் 02, 2021] Visuwesh wrote:
>
>> `recover-this-file' quite helpfully shows the time of creation of the
>> auto-save file.  However, this is not always enough to decide whether I
>> should recover from said auto-save file since there's no way of knowing
>> if the changes in auto-save file are desirable [1] so I end up answering
>> yes, then run `diff-buffer-with-file' anyway.  I think having a
>> `diff-buffer-with-file' option like `save-some-buffers' would be a
>> quality-of-life improvement.
>
> Please find attached path that uses read-answer to present the diff.

I didn't notice that recover-file was covered in the Emacs manual, I
have now updated the manual and marked the NEWS entry accordingly in the
attached patch.


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From 60d90c030a5b9a86a778df8650a597e922f2a907 Mon Sep 17 00:00:00 2001
From: Visuwesh <visuweshm@gmail.com>
Date: Wed, 6 Dec 2023 13:45:03 +0530
Subject: [PATCH] Offer to show diff against auto-save in recover-file

* lisp/files.el (recover-file): Show diff against the selected auto
save file.  (Bug#52242)

* doc/emacs/files.texi (Recover): Document the new feature.

* etc/NEWS: Announce the new feature.
---
 doc/emacs/files.texi |  8 +++++---
 etc/NEWS             |  5 +++++
 lisp/files.el        | 10 +++++++++-
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/doc/emacs/files.texi b/doc/emacs/files.texi
index 917e937d32d..c791a6f1c98 100644
--- a/doc/emacs/files.texi
+++ b/doc/emacs/files.texi
@@ -1325,9 +1325,11 @@ Recover
 @end example
 
   Before asking for confirmation, @kbd{M-x recover-file} displays a
-directory listing describing the specified file and the auto-save file,
-so you can compare their sizes and dates.  If the auto-save file
-is older, @kbd{M-x recover-file} does not offer to read it.
+directory listing describing the specified file and the auto-save
+file, so you can compare their sizes and dates.  If you answer
+@kbd{diff}, it shows the diff between @var{file} and its auto-save
+file @file{#@var{file}#}.  If the auto-save file is older, @kbd{M-x
+recover-file} does not offer to read it.
 
 @findex recover-session
   If Emacs or the computer crashes, you can recover all the files you
diff --git a/etc/NEWS b/etc/NEWS
index 29f4e5c0b66..f69595ef188 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -258,6 +258,11 @@ called in the '--eval' expression, which is useful when those
 arguments contain arbitrary characters that otherwise might require
 elaborate and error-prone escaping (to protect them from the shell).
 
++++
+** 'recover-file' can show diff between auto save file and current file.
+When answering the prompt with "diff" or "=", it now shows the diff
+between the auto save file and the current file.
+
 \f
 * Editing Changes in Emacs 30.1
 
diff --git a/lisp/files.el b/lisp/files.el
index 1cdcec23b11..d70524e4775 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -7083,7 +7083,15 @@ recover-file
 	    #'(lambda (window _value)
 		(with-selected-window window
 		  (unwind-protect
-		      (yes-or-no-p (format "Recover auto save file %s? " file-name))
+                      (let ((prompt (format "Recover auto save file %s? " file-name))
+                            (choices
+                             '(("yes" ?y "recover auto save file")
+                               ("no" ?n "don't recover auto save file")
+                               ("diff" ?= "diff auto save file with current file")))
+                            ans)
+                        (while (equal "diff" (setq ans (read-answer prompt choices)))
+                          (diff file file-name))
+                        (equal ans "yes"))
 		    (when (window-live-p window)
 		      (quit-restore-window window 'kill)))))
 	    (with-current-buffer standard-output
-- 
2.42.0

bug#52242: 29.0.50; Feature Request: Offer to run`diff-buffer-with-file' in `recover-this-file' prompt

[Eli Zaretskii]

> From: Visuwesh <visuweshm@gmail.com>
> Date: Thu, 07 Dec 2023 11:02:28 +0530
> 
> I didn't notice that recover-file was covered in the Emacs manual, I
> have now updated the manual and marked the NEWS entry accordingly in the
> attached patch.

Thanks, I have a few comments:

> diff --git a/doc/emacs/files.texi b/doc/emacs/files.texi
> index 917e937d32d..c791a6f1c98 100644
> --- a/doc/emacs/files.texi
> +++ b/doc/emacs/files.texi
> @@ -1325,9 +1325,11 @@ Recover
>  @end example
>  
>    Before asking for confirmation, @kbd{M-x recover-file} displays a
> -directory listing describing the specified file and the auto-save file,
> -so you can compare their sizes and dates.  If the auto-save file
> -is older, @kbd{M-x recover-file} does not offer to read it.
> +directory listing describing the specified file and the auto-save
> +file, so you can compare their sizes and dates.  If you answer
> +@kbd{diff}, it shows the diff between @var{file} and its auto-save
> +file @file{#@var{file}#}.  If the auto-save file is older, @kbd{M-x
> +recover-file} does not offer to read it.

It is better to make the documentation of the 'diff' response separate
from the rest, since the original text doesn't describe the responses
at all, it only mentions the need for confirmation.

So I suggest to leave the text starting at "Before asking for
confirmation" alone, and add a new paragraph after that one, like
this:

  When @kbd{M-x recover-file} asks for confirmation, if you respond
  with @kbd{diff} or @kbd{=}, it shows the diffs between ...

> ++++
> +** 'recover-file' can show diff between auto save file and current file.
                              ^^^^
We use "diffs", plural.

> +When answering the prompt with "diff" or "=", it now shows the diff
                                                                  ^^^^
Same here.

> +between the auto save file and the current file.
> +                            (choices
> +                             '(("yes" ?y "recover auto save file")
> +                               ("no" ?n "don't recover auto save file")
> +                               ("diff" ?= "diff auto save file with current file")))
                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Maybe a better text would be

   show changes between auto save file and current file

> +                            ans)
> +                        (while (equal "diff" (setq ans (read-answer prompt choices)))
> +                          (diff file file-name))
> +                        (equal ans "yes"))

Thanks.

bug#52242: 29.0.50; Feature Request: Offer to run`diff-buffer-with-file' in `recover-this-file' prompt

[Visuwesh]

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[சனி டிசம்பர் 09, 2023] Eli Zaretskii wrote:

>> From: Visuwesh <visuweshm@gmail.com>
>> Date: Thu, 07 Dec 2023 11:02:28 +0530
>> 
>> I didn't notice that recover-file was covered in the Emacs manual, I
>> have now updated the manual and marked the NEWS entry accordingly in the
>> attached patch.
>
> Thanks, I have a few comments:

Thanks for the review.

>> diff --git a/doc/emacs/files.texi b/doc/emacs/files.texi
>> index 917e937d32d..c791a6f1c98 100644
>> --- a/doc/emacs/files.texi
>> +++ b/doc/emacs/files.texi
>> @@ -1325,9 +1325,11 @@ Recover
>>  @end example
>>  
>>    Before asking for confirmation, @kbd{M-x recover-file} displays a
>> -directory listing describing the specified file and the auto-save file,
>> -so you can compare their sizes and dates.  If the auto-save file
>> -is older, @kbd{M-x recover-file} does not offer to read it.
>> +directory listing describing the specified file and the auto-save
>> +file, so you can compare their sizes and dates.  If you answer
>> +@kbd{diff}, it shows the diff between @var{file} and its auto-save
>> +file @file{#@var{file}#}.  If the auto-save file is older, @kbd{M-x
>> +recover-file} does not offer to read it.
>
> It is better to make the documentation of the 'diff' response separate
> from the rest, since the original text doesn't describe the responses
> at all, it only mentions the need for confirmation.
>
> So I suggest to leave the text starting at "Before asking for
> confirmation" alone, and add a new paragraph after that one, like
> this:
>
>   When @kbd{M-x recover-file} asks for confirmation, if you respond
>   with @kbd{diff} or @kbd{=}, it shows the diffs between ...

OK, I made it into a separate paragraph and added that it reprompts for
confirmation.

>> ++++
>> +** 'recover-file' can show diff between auto save file and current file.
>                               ^^^^
> We use "diffs", plural.
>
>> +When answering the prompt with "diff" or "=", it now shows the diff
>                                                                   ^^^^
> Same here.

Done.

>> +between the auto save file and the current file.
>> +                            (choices
>> +                             '(("yes" ?y "recover auto save file")
>> +                               ("no" ?n "don't recover auto save file")
>> +                               ("diff" ?= "diff auto save file with current file")))
>                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Maybe a better text would be
>
>    show changes between auto save file and current file

Thank you, that is indeed clear.  I have now changed the help text to
your suggestion.



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From 49105b0b98c6cccfda028f2ed52fe3cbd403028b Mon Sep 17 00:00:00 2001
From: Visuwesh <visuweshm@gmail.com>
Date: Wed, 6 Dec 2023 13:45:03 +0530
Subject: [PATCH] Offer to show diff against auto-save in recover-file

* lisp/files.el (recover-file): Show diff against the selected auto
save file.  (Bug#52242)

* doc/emacs/files.texi (Recover): Document the new feature.

* etc/NEWS: Announce the new feature.
---
 doc/emacs/files.texi |  8 ++++++--
 etc/NEWS             |  5 +++++
 lisp/files.el        | 10 +++++++++-
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/doc/emacs/files.texi b/doc/emacs/files.texi
index 917e937d32d..2fc1550de61 100644
--- a/doc/emacs/files.texi
+++ b/doc/emacs/files.texi
@@ -1325,10 +1325,14 @@ Recover
 @end example
 
   Before asking for confirmation, @kbd{M-x recover-file} displays a
-directory listing describing the specified file and the auto-save file,
-so you can compare their sizes and dates.  If the auto-save file
+directory listing describing the specified file and the auto-save
+file, so you can compare their sizes and dates.  If the auto-save file
 is older, @kbd{M-x recover-file} does not offer to read it.
 
+When @kbd{M-x recover-file} asks for confirmation, if you answer with
+@kbd{diff} or @kbd{=}, it shows the diffs between @var{file} and its
+auto-save file @file{#@var{file}#} and reprompts you for confirmation.
+
 @findex recover-session
   If Emacs or the computer crashes, you can recover all the files you
 were editing from their auto save files with the command @kbd{M-x
diff --git a/etc/NEWS b/etc/NEWS
index 29f4e5c0b66..39708d866d3 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -258,6 +258,11 @@ called in the '--eval' expression, which is useful when those
 arguments contain arbitrary characters that otherwise might require
 elaborate and error-prone escaping (to protect them from the shell).
 
++++
+** 'recover-file' can show diffs between auto save file and current file.
+When answering the prompt with "diff" or "=", it now shows the diffs
+between the auto save file and the current file.
+
 \f
 * Editing Changes in Emacs 30.1
 
diff --git a/lisp/files.el b/lisp/files.el
index 1cdcec23b11..83534e0080c 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -7083,7 +7083,15 @@ recover-file
 	    #'(lambda (window _value)
 		(with-selected-window window
 		  (unwind-protect
-		      (yes-or-no-p (format "Recover auto save file %s? " file-name))
+                      (let ((prompt (format "Recover auto save file %s? " file-name))
+                            (choices
+                             '(("yes" ?y "recover auto save file")
+                               ("no" ?n "don't recover auto save file")
+                               ("diff" ?= "show changes between auto save file and current file")))
+                            ans)
+                        (while (equal "diff" (setq ans (read-answer prompt choices)))
+                          (diff file file-name))
+                        (equal ans "yes"))
 		    (when (window-live-p window)
 		      (quit-restore-window window 'kill)))))
 	    (with-current-buffer standard-output
-- 
2.42.0

bug#52242: 29.0.50; Feature Request: Offer to run`diff-buffer-with-file' in `recover-this-file' prompt

[Visuwesh]

[-- Attachment #1: Type: text/plain, Size: 193 bytes --]

[ஞாயிறு டிசம்பர் 10, 2023] Visuwesh wrote:

Just noticed that I had an unrelated filling change sneak in, the
attached patch omits that.  Sorry for the noise.


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-Offer-to-show-diff-against-auto-save-in-recover-file.patch --]
[-- Type: text/x-diff, Size: 2853 bytes --]

From d4ce87ae26c3c43851841432d4f3e1b3f5404f75 Mon Sep 17 00:00:00 2001
From: Visuwesh <visuweshm@gmail.com>
Date: Wed, 6 Dec 2023 13:45:03 +0530
Subject: [PATCH] Offer to show diff against auto-save in recover-file

* lisp/files.el (recover-file): Show diff against the selected auto
save file.  (Bug#52242)

* doc/emacs/files.texi (Recover): Document the new feature.

* etc/NEWS: Announce the new feature.
---
 doc/emacs/files.texi |  4 ++++
 etc/NEWS             |  5 +++++
 lisp/files.el        | 10 +++++++++-
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/doc/emacs/files.texi b/doc/emacs/files.texi
index 917e937d32d..832c189ce49 100644
--- a/doc/emacs/files.texi
+++ b/doc/emacs/files.texi
@@ -1329,6 +1329,10 @@ Recover
 so you can compare their sizes and dates.  If the auto-save file
 is older, @kbd{M-x recover-file} does not offer to read it.
 
+When @kbd{M-x recover-file} asks for confirmation, if you answer with
+@kbd{diff} or @kbd{=}, it shows the diffs between @var{file} and its
+auto-save file @file{#@var{file}#} and reprompts you for confirmation.
+
 @findex recover-session
   If Emacs or the computer crashes, you can recover all the files you
 were editing from their auto save files with the command @kbd{M-x
diff --git a/etc/NEWS b/etc/NEWS
index 29f4e5c0b66..39708d866d3 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -258,6 +258,11 @@ called in the '--eval' expression, which is useful when those
 arguments contain arbitrary characters that otherwise might require
 elaborate and error-prone escaping (to protect them from the shell).
 
++++
+** 'recover-file' can show diffs between auto save file and current file.
+When answering the prompt with "diff" or "=", it now shows the diffs
+between the auto save file and the current file.
+
 \f
 * Editing Changes in Emacs 30.1
 
diff --git a/lisp/files.el b/lisp/files.el
index 1cdcec23b11..83534e0080c 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -7083,7 +7083,15 @@ recover-file
 	    #'(lambda (window _value)
 		(with-selected-window window
 		  (unwind-protect
-		      (yes-or-no-p (format "Recover auto save file %s? " file-name))
+                      (let ((prompt (format "Recover auto save file %s? " file-name))
+                            (choices
+                             '(("yes" ?y "recover auto save file")
+                               ("no" ?n "don't recover auto save file")
+                               ("diff" ?= "show changes between auto save file and current file")))
+                            ans)
+                        (while (equal "diff" (setq ans (read-answer prompt choices)))
+                          (diff file file-name))
+                        (equal ans "yes"))
 		    (when (window-live-p window)
 		      (quit-restore-window window 'kill)))))
 	    (with-current-buffer standard-output
-- 
2.42.0

bug#52242: 29.0.50; Feature Request: Offer to run`diff-buffer-with-file' in `recover-this-file' prompt

[Eli Zaretskii]

> From: Visuwesh <visuweshm@gmail.com>
> Cc: 52242@debbugs.gnu.org
> Date: Mon, 11 Dec 2023 09:44:50 +0530
> 
> [ஞாயிறு டிசம்பர் 10, 2023] Visuwesh wrote:
> 
> Just noticed that I had an unrelated filling change sneak in, the
> attached patch omits that.  Sorry for the noise.

Thanks, installed on the master branch, and closing the bug.