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Re: Don't complain about changed file when it hasn't changed
From: |
Stefan Monnier |
Subject: |
Re: Don't complain about changed file when it hasn't changed |
Date: |
Mon, 29 Aug 2016 12:01:55 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) |
> Anyway, the proposed implementation misses a few subtleties, IMO:
Revised patch,
Stefan
diff --git a/etc/NEWS b/etc/NEWS
index 1290fa4..cdabeda 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -213,6 +213,10 @@ In modes where form feed was treated as a whitespace
character,
It now deletes whitespace after the last form feed thus behaving the
same as in modes where the character is not whitespace.
+** No more prompt about changed file when the file's content is unchanged.
+Instead of only checking the modification time, Emacs now also checks
+the file's actual content before prompting the user.
+
* Changes in Specialized Modes and Packages in Emacs 25.2
diff --git a/lisp/userlock.el b/lisp/userlock.el
index a0c55fd..2295184 100644
--- a/lisp/userlock.el
+++ b/lisp/userlock.el
@@ -97,6 +97,28 @@ ask-user-about-lock-help
(define-error 'file-supersession nil 'file-error)
+(defun userlock--check-content-unchanged (fn)
+ (with-demoted-errors "Unchanged content check: %S"
+ (save-restriction
+ (widen)
+ (let ((buf (current-buffer))
+ (cs buffer-file-coding-system)
+ (start (point-min))
+ (end (point-max)))
+ ;; FIXME: To avoid a slow `insert-file-contents' on large or
+ ;; remote files, it'd be good to include file size in the
+ ;; "visited-modtime" check.
+ (when (with-temp-buffer
+ (let ((coding-system-for-read cs))
+ (insert-file-contents fn))
+ (when (= (buffer-size) (- end start)) ;Minor optimization.
+ (= 0 (let ((case-fold-search nil))
+ (compare-buffer-substrings
+ buf start end
+ (current-buffer) (point-min) (point-max))))))
+ (set-visited-file-modtime)
+ 'unchanged)))))
+
;;;###autoload
(defun ask-user-about-supersession-threat (fn)
"Ask a user who is about to modify an obsolete buffer what to do.
@@ -106,30 +128,30 @@ ask-user-about-supersession-threat
You can rewrite this to use any criterion you like to choose which one to do.
The buffer in question is current when this function is called."
- (discard-input)
- (save-window-excursion
- (let ((prompt
- (format "%s changed on disk; \
+ (unless (userlock--check-content-unchanged fn)
+ (discard-input)
+ (save-window-excursion
+ (let ((prompt
+ (format "%s changed on disk; \
really edit the buffer? (y, n, r or C-h) "
- (file-name-nondirectory fn)))
- (choices '(?y ?n ?r ?? ?\C-h))
- answer)
- (while (null answer)
- (setq answer (read-char-choice prompt choices))
- (cond ((memq answer '(?? ?\C-h))
- (ask-user-about-supersession-help)
- (setq answer nil))
- ((eq answer ?r)
- ;; Ask for confirmation if buffer modified
- (revert-buffer nil (not (buffer-modified-p)))
- (signal 'file-supersession
- (list "File reverted" fn)))
- ((eq answer ?n)
- (signal 'file-supersession
- (list "File changed on disk" fn)))))
- (message
- "File on disk now will become a backup file if you save these changes.")
- (setq buffer-backed-up nil))))
+ (file-name-nondirectory fn))))
+ (while
+ (let ((answer (read-char-choice prompt '(?y ?n ?r ?? ?\C-h))))
+ (cond ((memq answer '(?? ?\C-h))
+ (ask-user-about-supersession-help)
+ 'repeat)
+ ((eq answer ?r)
+ ;; Ask for confirmation if buffer modified
+ (revert-buffer nil (not (buffer-modified-p)))
+ (signal 'file-supersession
+ (list "File reverted" fn)))
+ ((eq answer ?n)
+ (signal 'file-supersession
+ (list "File changed on disk" fn)))
+ (t (null answer)))))
+ (message
+ "File on disk now will become a backup file if you save these
changes.")
+ (setq buffer-backed-up nil)))))
(defun ask-user-about-supersession-help ()
(with-output-to-temp-buffer "*Help*"
- Re: Don't complain about changed file when it hasn't changed, (continued)
- Re: Don't complain about changed file when it hasn't changed, Clément Pit--Claudel, 2016/08/30
- Re: Don't complain about changed file when it hasn't changed, Stefan Monnier, 2016/08/30
- Re: Don't complain about changed file when it hasn't changed, Clément Pit--Claudel, 2016/08/30
- Re: Don't complain about changed file when it hasn't changed, Eli Zaretskii, 2016/08/30
- Re: Don't complain about changed file when it hasn't changed, Clément Pit--Claudel, 2016/08/30
- Re: Don't complain about changed file when it hasn't changed, Stefan Monnier, 2016/08/30
- Re: Don't complain about changed file when it hasn't changed, Eli Zaretskii, 2016/08/30
Re: Don't complain about changed file when it hasn't changed, Eli Zaretskii, 2016/08/29
- Re: Don't complain about changed file when it hasn't changed,
Stefan Monnier <=
Re: Don't complain about changed file when it hasn't changed, Davis Herring, 2016/08/29
Re: Don't complain about changed file when it hasn't changed, Stefan Monnier, 2016/08/29
Re: Don't complain about changed file when it hasn't changed, Rolf Ade, 2016/08/30