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a6a92e3ac5
* lisp/files.el (make-lock-file-name): Fix docstring. * lisp/net/tramp-adb.el (tramp-adb-file-name-handler-alist): * lisp/net/tramp-archive.el (tramp-archive-file-name-handler-alist): * lisp/net/tramp-crypt.el (tramp-crypt-file-name-handler-alist): * lisp/net/tramp-gvfs.el (tramp-gvfs-file-name-handler-alist): * lisp/net/tramp-rclone.el (tramp-rclone-file-name-handler-alist): * lisp/net/tramp-sh.el (tramp-sh-file-name-handler-alist): * lisp/net/tramp-smb.el (tramp-smb-file-name-handler-alist): * lisp/net/tramp-sshfs.el (tramp-sshfs-file-name-handler-alist): * lisp/net/tramp-sudoedit.el (tramp-sudoedit-file-name-handler-alist): Add `make-lock-file-name'. * lisp/net/tramp.el (tramp-file-name-for-operation): Add `make-lock-file-name'. (tramp-handle-unlock-file): Call `userlock--handle-unlock-error' in case of error. * src/buffer.c (Frestore_buffer_modified_p): * src/editfns.c (Freplace_buffer_contents): * src/fileio.c (Finsert_file_contents, write_region): Call Funlock_file. * src/filelock.c (unlock_file): Rename from unlock_file_body. Remove the other declarations of unlock_file. Move file name handler check to ... (Funlock_file): ... here. Adapt argument numbers. Call unlock_file wrapped by internal_condition_case. (Flock_file): Adapt argument numbers. (unlock_all_files, Funlock_buffer, unlock_buffer): Call Funlock_file. * src/lisp.h (unlock_file): Remove.
238 lines
8.9 KiB
EmacsLisp
238 lines
8.9 KiB
EmacsLisp
;;; userlock.el --- handle file access contention between multiple users -*- lexical-binding: t -*-
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;; Copyright (C) 1985-1986, 2001-2021 Free Software Foundation, Inc.
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;; Author: Richard King
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;; (according to authors.el)
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;; Maintainer: emacs-devel@gnu.org
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;; Keywords: internal
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;; Package: emacs
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:
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;; This file is autoloaded to handle certain conditions
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;; detected by the file-locking code within Emacs.
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;; The two entry points are `ask-user-about-lock' and
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;; `ask-user-about-supersession-threat'.
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;;; Code:
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(eval-when-compile (require 'cl-lib))
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;;;###autoload
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(put 'create-lockfiles 'safe-local-variable 'booleanp)
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(define-error 'file-locked "File is locked" 'file-error)
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(defun userlock--fontify-key (key)
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"Add the `help-key-binding' face to string KEY."
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(propertize key 'face 'help-key-binding))
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;;;###autoload
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(defun ask-user-about-lock (file opponent)
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"Ask user what to do when he wants to edit FILE but it is locked by OPPONENT.
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This function has a choice of three things to do:
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do (signal \\='file-locked (list FILE OPPONENT))
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to refrain from editing the file
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return t (grab the lock on the file)
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return nil (edit the file even though it is locked).
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You can redefine this function to choose among those three alternatives
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in any way you like."
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(discard-input)
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(save-window-excursion
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(let (answer short-opponent short-file)
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(setq short-file
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(if (> (length file) 22)
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(concat "..." (substring file (- (length file) 22)))
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file))
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(setq short-opponent
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(if (> (length opponent) 25)
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(save-match-data
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(string-match " (pid [0-9]+)" opponent)
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(concat (substring opponent 0 13) "..."
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(match-string 0 opponent)))
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opponent))
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(while (null answer)
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(message "%s locked by %s: (%s, %s, %s, %s)? "
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short-file short-opponent
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(userlock--fontify-key "s")
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(userlock--fontify-key "q")
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(userlock--fontify-key "p")
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(userlock--fontify-key "?"))
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(if noninteractive (error "Cannot resolve lock conflict in batch mode"))
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(let ((tem (let ((inhibit-quit t)
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(cursor-in-echo-area t))
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(prog1 (downcase (read-char))
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(setq quit-flag nil)))))
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(if (= tem help-char)
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(ask-user-about-lock-help)
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(setq answer (assoc tem '((?s . t)
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(?q . yield)
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(?\C-g . yield)
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(?p . nil)
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(?? . help))))
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(cond ((null answer)
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(beep)
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(message "Please type %s, %s, or %s; or %s for help"
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(userlock--fontify-key "q")
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(userlock--fontify-key "s")
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(userlock--fontify-key "p")
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;; FIXME: Why do we use "?" here and "C-h" below?
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(userlock--fontify-key "?"))
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(sit-for 3))
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((eq (cdr answer) 'help)
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(ask-user-about-lock-help)
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(setq answer nil))
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((eq (cdr answer) 'yield)
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(signal 'file-locked (list file opponent)))))))
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(cdr answer))))
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(defun ask-user-about-lock-help ()
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(with-output-to-temp-buffer "*Help*"
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(with-current-buffer standard-output
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(insert
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(format
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"It has been detected that you want to modify a file that someone else has
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already started modifying in Emacs.
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You can <%s>teal the file; the other user becomes the
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intruder if (s)he ever unmodifies the file and then changes it again.
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You can <%s>roceed; you edit at your own (and the other user's) risk.
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You can <%s>uit; don't modify this file."
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(userlock--fontify-key "s")
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(userlock--fontify-key "p")
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(userlock--fontify-key "q")))
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(help-mode))))
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(define-error 'file-supersession nil 'file-error)
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(defun userlock--check-content-unchanged (filename)
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(with-demoted-errors "Unchanged content check: %S"
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;; Even tho we receive `filename', we know that `filename' refers to the current
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;; buffer's file.
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(cl-assert (equal filename (expand-file-name buffer-file-truename)))
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;; Note: rather than read the file and compare to the buffer, we could save
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;; the buffer and compare to the file, but for encrypted data this
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;; wouldn't work well (and would risk exposing the data).
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(save-restriction
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(widen)
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(let ((buf (current-buffer))
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(cs buffer-file-coding-system)
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(start (point-min))
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(end (point-max)))
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;; FIXME: To avoid a slow `insert-file-contents' on large or
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;; remote files, it'd be good to include file size in the
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;; "visited-modtime" check.
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(when (with-temp-buffer
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(let ((coding-system-for-read cs)
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(non-essential t))
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(insert-file-contents filename))
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(when (= (buffer-size) (- end start)) ;Minor optimization.
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(= 0 (let ((case-fold-search nil))
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(compare-buffer-substrings
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buf start end
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(current-buffer) (point-min) (point-max))))))
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(set-visited-file-modtime)
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'unchanged)))))
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;;;###autoload
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(defun userlock--ask-user-about-supersession-threat (filename)
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;; Called from filelock.c.
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(unless (userlock--check-content-unchanged filename)
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(ask-user-about-supersession-threat filename)))
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;;;###autoload
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(defun ask-user-about-supersession-threat (filename)
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"Ask a user who is about to modify an obsolete buffer what to do.
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This function has two choices: it can return, in which case the modification
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of the buffer will proceed, or it can (signal \\='file-supersession (file)),
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in which case the proposed buffer modification will not be made.
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You can rewrite this to use any criterion you like to choose which one to do.
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The buffer in question is current when this function is called."
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(discard-input)
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(save-window-excursion
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(let ((prompt
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(format "%s changed on disk; \
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really edit the buffer? (%s, %s, %s or %s) "
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(file-name-nondirectory filename)
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(userlock--fontify-key "y")
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(userlock--fontify-key "n")
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(userlock--fontify-key "r")
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;; FIXME: Why do we use "C-h" here and "?" above?
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(userlock--fontify-key "C-h")))
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(choices '(?y ?n ?r ?? ?\C-h))
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answer)
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(when noninteractive
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(message "%s" prompt)
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(error "Cannot resolve conflict in batch mode"))
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(while (null answer)
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(setq answer (read-char-choice prompt choices))
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(cond ((memq answer '(?? ?\C-h))
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(ask-user-about-supersession-help)
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(setq answer nil))
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((eq answer ?r)
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;; Ask for confirmation if buffer modified
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(revert-buffer nil (not (buffer-modified-p)))
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(signal 'file-supersession
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(list "File reverted" filename)))
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((eq answer ?n)
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(signal 'file-supersession
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(list "File changed on disk" filename)))))
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(message
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"File on disk now will become a backup file if you save these changes.")
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(setq buffer-backed-up nil))))
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(defun ask-user-about-supersession-help ()
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(with-output-to-temp-buffer "*Help*"
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(let ((revert-buffer-binding
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;; This takes place in the original buffer.
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(substitute-command-keys "\\[revert-buffer]")))
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(with-current-buffer standard-output
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(insert
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(format
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"You want to modify a buffer whose disk file has changed
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since you last read it in or saved it with this buffer.
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If you say %s to go ahead and modify this buffer,
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you risk ruining the work of whoever rewrote the file.
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If you say %s to revert, the contents of the buffer are refreshed
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from the file on disk.
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If you say %s, the change you started to make will be aborted.
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Usually, you should type %s and then %s,
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to get the latest version of the file, then make the change again."
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(userlock--fontify-key "y")
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(userlock--fontify-key "r")
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(userlock--fontify-key "n")
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(userlock--fontify-key "n")
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revert-buffer-binding))
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(help-mode)))))
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;;;###autoload
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(defun userlock--handle-unlock-error (error)
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"Report an ERROR that occurred while unlocking a file."
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(display-warning
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'(unlock-file)
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;; There is no need to explain that this is an unlock error because
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;; ERROR is a `file-error' condition, which explains this.
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(message "%s, ignored" (error-message-string error))
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:warning))
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;;; userlock.el ends here
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