lisp/vc/diff.el

   1 ;;; diff.el --- run `diff'  -*- lexical-binding: t -*-
   2
   3 ;; Copyright (C) 1992, 1994, 1996, 2001-2017 Free Software Foundation,
   4 ;; Inc.
   5
   6 ;; Author: Frank Bresz
   7 ;; (according to authors.el)
   8 ;; Maintainer: emacs-devel@gnu.org
   9 ;; Keywords: unix, vc, tools
  10
  11 ;; This file is part of GNU Emacs.
  12
  13 ;; GNU Emacs is free software: you can redistribute it and/or modify
  14 ;; it under the terms of the GNU General Public License as published by
  15 ;; the Free Software Foundation, either version 3 of the License, or
  16 ;; (at your option) any later version.
  17
  18 ;; GNU Emacs is distributed in the hope that it will be useful,
  19 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 ;; GNU General Public License for more details.
  22
  23 ;; You should have received a copy of the GNU General Public License
  24 ;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
  25
  26 ;;; Commentary:
  27
  28 ;; This package helps you explore differences between files, using the
  29 ;; UNIX command diff(1).  The commands are `diff' and `diff-backup'.
  30 ;; You can specify options with `diff-switches'.
  31
  32 ;;; Code:
  33
  34 (declare-function diff-setup-whitespace "diff-mode" ())
  35
  36 (defgroup diff nil
  37   "Comparing files with `diff'."
  38   :group 'tools)
  39
  40 ;;;###autoload
  41 (defcustom diff-switches (purecopy "-u")
  42   "A string or list of strings specifying switches to be passed to diff."
  43   :type '(choice string (repeat string))
  44   :group 'diff)
  45
  46 ;;;###autoload
  47 (defcustom diff-command (purecopy "diff")
  48   "The command to use to run diff."
  49   :type 'string
  50   :group 'diff)
  51
  52 ;; prompt if prefix arg present
  53 (defun diff-switches ()
  54   (if current-prefix-arg
  55       (read-string "Diff switches: "
  56                    (if (stringp diff-switches)
  57                        diff-switches
  58                      (mapconcat 'identity diff-switches " ")))))
  59
  60 (defun diff-sentinel (code &optional old-temp-file new-temp-file)
  61   "Code run when the diff process exits.
  62 CODE is the exit code of the process.  It should be 0 only if no diffs
  63 were found.
  64 If optional args OLD-TEMP-FILE and/or NEW-TEMP-FILE are non-nil,
  65 delete the temporary files so named."
  66   (if old-temp-file (delete-file old-temp-file))
  67   (if new-temp-file (delete-file new-temp-file))
  68   (diff-setup-whitespace)
  69   (goto-char (point-min))
  70   (save-excursion
  71     (goto-char (point-max))
  72     (let ((inhibit-read-only t))
  73       (insert (format "\nDiff finished%s.  %s\n"
  74                       (cond ((equal 0 code) " (no differences)")
  75                             ((equal 2 code) " (diff error)")
  76                             (t ""))
  77                       (current-time-string))))))
  78
  79 ;;;###autoload
  80 (defun diff (old new &optional switches no-async)
  81   "Find and display the differences between OLD and NEW files.
  82 When called interactively, read NEW, then OLD, using the
  83 minibuffer.  The default for NEW is the current buffer's file
  84 name, and the default for OLD is a backup file for NEW, if one
  85 exists.  If NO-ASYNC is non-nil, call diff synchronously.
  86
  87 When called interactively with a prefix argument, prompt
  88 interactively for diff switches.  Otherwise, the switches
  89 specified in the variable `diff-switches' are passed to the diff command."
  90   (interactive
  91    (let* ((newf (if (and buffer-file-name (file-exists-p buffer-file-name))
  92                     (read-file-name
  93                      (concat "Diff new file (default "
  94                              (file-name-nondirectory buffer-file-name) "): ")
  95                      nil buffer-file-name t)
  96                   (read-file-name "Diff new file: " nil nil t)))
  97           (oldf (file-newest-backup newf)))
  98      (setq oldf (if (and oldf (file-exists-p oldf))
  99                     (read-file-name
 100                      (concat "Diff original file (default "
 101                              (file-name-nondirectory oldf) "): ")
 102                      (file-name-directory oldf) oldf t)
 103                   (read-file-name "Diff original file: "
 104                                   (file-name-directory newf) nil t)))
 105      (list oldf newf (diff-switches))))
 106   (display-buffer
 107    (diff-no-select old new switches no-async)))
 108
 109 (defun diff-file-local-copy (file-or-buf)
 110   (if (bufferp file-or-buf)
 111       (with-current-buffer file-or-buf
 112         (let ((tempfile (make-temp-file "buffer-content-")))
 113           (write-region nil nil tempfile nil 'nomessage)
 114           tempfile))
 115     (file-local-copy file-or-buf)))
 116
 117 (defvar diff-use-labels 'check
 118   "Whether `diff-command' understands the \"--label\" option.
 119 Possible values are:
 120   t     -- yes, it does
 121   nil   -- no, it does not
 122   check -- try to probe whether it does")
 123
 124 (defun diff-no-select (old new &optional switches no-async buf)
 125   ;; Noninteractive helper for creating and reverting diff buffers
 126   (unless (bufferp new) (setq new (expand-file-name new)))
 127   (unless (bufferp old) (setq old (expand-file-name old)))
 128   (or switches (setq switches diff-switches)) ; If not specified, use default.
 129   (unless (listp switches) (setq switches (list switches)))
 130   (or buf (setq buf (get-buffer-create "*Diff*")))
 131   (when (eq 'check diff-use-labels)
 132     (setq diff-use-labels
 133           (with-temp-buffer
 134             (when (ignore-errors (call-process diff-command nil t nil "--help"))
 135               (if (search-backward "--label" nil t) t)))))
 136   (let* ((old-alt (diff-file-local-copy old))
 137          (new-alt (diff-file-local-copy new))
 138          (command
 139           (mapconcat 'identity
 140                      `(,diff-command
 141                        ;; Use explicitly specified switches
 142                        ,@switches
 143                        ,@(mapcar #'shell-quote-argument
 144                                  (nconc
 145                                   (and (or old-alt new-alt)
 146                                        (eq diff-use-labels t)
 147                                        (list "--label"
 148                                              (if (stringp old) old
 149                                                (prin1-to-string old))
 150                                              "--label"
 151                                              (if (stringp new) new
 152                                                (prin1-to-string new))))
 153                                   (list (or old-alt old)
 154                                         (or new-alt new)))))
 155                      " "))
 156          (thisdir default-directory))
 157     (with-current-buffer buf
 158       (setq buffer-read-only t)
 159       (buffer-disable-undo (current-buffer))
 160       (let ((inhibit-read-only t))
 161         (erase-buffer))
 162       (buffer-enable-undo (current-buffer))
 163       (diff-mode)
 164       (set (make-local-variable 'revert-buffer-function)
 165            (lambda (_ignore-auto _noconfirm)
 166              (diff-no-select old new switches no-async (current-buffer))))
 167       (setq default-directory thisdir)
 168       (let ((inhibit-read-only t))
 169         (insert command "\n"))
 170       (if (and (not no-async) (fboundp 'make-process))
 171           (let ((proc (start-process "Diff" buf shell-file-name
 172                                      shell-command-switch command)))
 173             (set-process-filter proc 'diff-process-filter)
 174             (set-process-sentinel
 175              proc (lambda (proc _msg)
 176                     (with-current-buffer (process-buffer proc)
 177                       (diff-sentinel (process-exit-status proc)
 178                                      old-alt new-alt)))))
 179         ;; Async processes aren't available.
 180         (let ((inhibit-read-only t))
 181           (diff-sentinel
 182            (call-process shell-file-name nil buf nil
 183                          shell-command-switch command)
 184            old-alt new-alt))))
 185     buf))
 186
 187 (defun diff-process-filter (proc string)
 188   (with-current-buffer (process-buffer proc)
 189     (let ((moving (= (point) (process-mark proc))))
 190       (save-excursion
 191         ;; Insert the text, advancing the process marker.
 192         (goto-char (process-mark proc))
 193         (let ((inhibit-read-only t))
 194           (insert string))
 195         (set-marker (process-mark proc) (point)))
 196       (if moving (goto-char (process-mark proc))))))
 197
 198 ;;;###autoload
 199 (defun diff-backup (file &optional switches)
 200   "Diff this file with its backup file or vice versa.
 201 Uses the latest backup, if there are several numerical backups.
 202 If this file is a backup, diff it with its original.
 203 The backup file is the first file given to `diff'.
 204 With prefix arg, prompt for diff switches."
 205   (interactive (list (read-file-name "Diff (file with backup): ")
 206                      (diff-switches)))
 207   (let (bak ori)
 208     (if (backup-file-name-p file)
 209         (setq bak file
 210               ori (file-name-sans-versions file))
 211       (setq bak (or (diff-latest-backup-file file)
 212                     (error "No backup found for %s" file))
 213             ori file))
 214     (diff bak ori switches)))
 215
 216 ;;;###autoload
 217 (defun diff-latest-backup-file (fn)
 218   "Return the latest existing backup of FILE, or nil."
 219   (let ((handler (find-file-name-handler fn 'diff-latest-backup-file)))
 220     (if handler
 221         (funcall handler 'diff-latest-backup-file fn)
 222       (file-newest-backup fn))))
 223
 224 ;;;###autoload
 225 (defun diff-buffer-with-file (&optional buffer)
 226   "View the differences between BUFFER and its associated file.
 227 This requires the external program `diff' to be in your `exec-path'."
 228   (interactive "bBuffer: ")
 229   (with-current-buffer (get-buffer (or buffer (current-buffer)))
 230     (diff buffer-file-name (current-buffer) nil 'noasync)))
 231
 232 (provide 'diff)
 233
 234 ;;; diff.el ends here