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

[Visuwesh <visuweshm@gmail.com>]

[-- 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