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

[Visuwesh <visuweshm@gmail.com>]

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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