diff options
| -rw-r--r-- | doc/lispref/buffers.texi | 5 | ||||
| -rw-r--r-- | etc/NEWS | 4 | ||||
| -rw-r--r-- | lisp/userlock.el | 35 | ||||
| -rw-r--r-- | src/filelock.c | 2 |
4 files changed, 43 insertions, 3 deletions
diff --git a/doc/lispref/buffers.texi b/doc/lispref/buffers.texi index 740d7cfd8a..e4ef4d5db6 100644 --- a/doc/lispref/buffers.texi +++ b/doc/lispref/buffers.texi @@ -669,8 +669,9 @@ reason. This function is used to ask a user how to proceed after an attempt to modify an buffer visiting file @var{filename} when the file is newer than the buffer text. Emacs detects this because the modification -time of the file on disk is newer than the last save-time of the -buffer. This means some other program has probably altered the file. +time of the file on disk is newer than the last save-time and its contents +have changed. +This means some other program has probably altered the file. @kindex file-supersession Depending on the user's answer, the function may return normally, in @@ -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 a0c55fd1e1..1cfc3b9d64 100644 --- a/lisp/userlock.el +++ b/lisp/userlock.el @@ -97,6 +97,41 @@ You can <q>uit; don't modify this file.") (define-error 'file-supersession nil 'file-error) +(defun userlock--check-content-unchanged (fn) + (with-demoted-errors "Unchanged content check: %S" + ;; Even tho we receive `fn', we know that `fn' refers to the current + ;; buffer's file. + (cl-assert (equal fn (expand-file-name buffer-file-truename))) + ;; Note: rather than read the file and compare to the buffer, we could save + ;; the buffer and compare to the file, but for encrypted data this + ;; wouldn't work well (and would risk exposing the data). + (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) + (non-essential t)) + (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 userlock--ask-user-about-supersession-threat (fn) + ;; Called from filelock.c. + (unless (userlock--check-content-unchanged fn) + (ask-user-about-supersession-threat fn))) + ;;;###autoload (defun ask-user-about-supersession-threat (fn) "Ask a user who is about to modify an obsolete buffer what to do. diff --git a/src/filelock.c b/src/filelock.c index 2f92e0fdc8..bde34e2c6c 100644 --- a/src/filelock.c +++ b/src/filelock.c @@ -684,7 +684,7 @@ lock_file (Lisp_Object fn) if (!NILP (subject_buf) && NILP (Fverify_visited_file_modtime (subject_buf)) && !NILP (Ffile_exists_p (fn))) - call1 (intern ("ask-user-about-supersession-threat"), fn); + call1 (intern ("userlock--ask-user-about-supersession-threat"), fn); } |