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diff --git a/lisp/vc-hooks.el b/lisp/vc-hooks.el
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+;;; vc-hooks.el -- resident support for version-control
+
+;; Copyright (C) 1992 Free Software Foundation, Inc.
+
+;; Author: Eric S. Raymond <[email protected]>
+;; Version: 4.0
+
+;;	$Id: vc-hooks.el,v 1.44 1992/07/31 06:43:05 esr Exp $	
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 2, or (at your option)
+;; any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to
+;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+;;; Commentary:
+
+;; See the commentary of vc.el.
+
+;;; Code:
+
+(defvar vc-master-templates
+  '(("%sRCS/%s,v" . RCS) ("%s%s,v" . RCS) ("%sRCS/%s" . RCS)
+    ("%sSCCS/s.%s" . SCCS) ("%ss.%s". SCCS))
+  "*Where to look for version-control master files.
+The first pair corresponding to a given back end is used as a template
+when creating new masters.")
+
+(defvar vc-make-backup-files nil
+  "*If non-nil, backups of registered files are made according to
+the make-backup-files variable.  Otherwise, prevents backups being made.")
+
+;; Tell Emacs about this new kind of minor mode
+(if (not (assoc 'vc-mode-string minor-mode-alist))
+    (setq minor-mode-alist (cons '(vc-mode-string vc-mode-string)
+				 minor-mode-alist)))
+
+(make-variable-buffer-local 'vc-mode-string)
+
+;; We need a notion of per-file properties because the version
+;; control state of a file is expensive to derive --- we don't
+;; want to recompute it even on every find.
+
+(defvar vc-file-prop-obarray [0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]
+  "Obarray for per-file properties.")
+
+(defun vc-file-setprop (file property value)
+  ;; set per-file property
+  (put (intern file vc-file-prop-obarray) property value))
+
+(defun vc-file-getprop (file property)
+  ;; get per-file property
+  (get (intern file vc-file-prop-obarray) property))
+
+;;; actual version-control code starts here
+
+(defun vc-registered (file)
+  ;; Search for a master corresponding to the given file
+  (let ((dirname (or (file-name-directory file) ""))
+	(basename (file-name-nondirectory file)))
+    (catch 'found
+      (mapcar
+       (function (lambda (s)
+	  (let ((trial (format (car s) dirname basename)))
+	    (if (and (file-exists-p trial)
+		     ;; Make sure the file we found with name
+		     ;; TRIAL is not the source file itself.
+		     ;; That can happen with RCS-style names
+		     ;; if the file name is truncated
+		     ;; (e.g. to 14 chars).  See if either
+		     ;; directory or attributes differ.
+		     (or (not (string= dirname
+				       (file-name-directory trial)))
+			 (not (equal
+			       (file-attributes file)
+			       (file-attributes trial)))))
+		(throw 'found (cons trial (cdr s)))))))
+       vc-master-templates)
+      nil)
+    ))
+
+(defun vc-backend-deduce (file)
+  "Return the version-control type of a file, nil if it is not registered"
+  (and file
+       (or (vc-file-getprop file 'vc-backend)
+	   (vc-file-setprop file 'vc-backend (cdr (vc-registered file))))))
+
+(defun vc-toggle-read-only ()
+  "If the file in the current buffer id under version control, perform the
+logical next version-control action; otherwise, just toggle the buffer's
+read-only flag."
+  (interactive)
+  (if (vc-backend-deduce (buffer-file-name))
+      (vc-next-action nil)
+    (toggle-read-only)))
+
+(defun vc-mode-line (file &optional label)
+  "Set `vc-mode-string' to display type of version control for FILE.
+The value is set in the current buffer, which should be the buffer
+visiting FILE."
+  (let ((vc-type (vc-backend-deduce file)))
+    (if vc-type
+	(progn
+	  (if (null (current-local-map))
+	      (use-local-map (make-sparse-keymap)))
+	  (define-key (current-local-map) "\C-x\C-q" 'vc-toggle-read-only)
+	  (setq vc-mode-string
+		(concat " " (or label (symbol-name vc-type))))))
+    ;; force update of mode line
+    (set-buffer-modified-p (buffer-modified-p))
+    vc-type))
+
+;;; install a call to the above as a find-file hook
+(defun vc-find-file-hook ()
+  (if (and (vc-mode-line buffer-file-name) (not vc-make-backup-files))
+      (progn
+	(make-local-variable 'make-backup-files)
+	(setq make-backup-files nil))))
+
+(or (memq 'vc-find-file-hook find-file-hooks)
+    (setq find-file-hooks
+	  (cons 'vc-find-file-hook find-file-hooks)))
+
+;;; more hooks, this time for file-not-found
+(defun vc-file-not-found-hook ()
+  "When file is not found, try to check it out from RCS or SCCS.
+Returns t if checkout was successful, nil otherwise."
+  (if (vc-backend-deduce buffer-file-name)
+      (progn
+	(require 'vc)
+	(not (vc-error-occurred (vc-checkout buffer-file-name))))))
+
+(or (memq 'vc-file-not-found-hook find-file-not-found-hooks)
+    (setq find-file-not-found-hooks
+	  (cons 'vc-file-not-found-hook find-file-not-found-hooks)))
+
+;;; Now arrange for bindings and autoloading of the main package.
+;;; Bindings for this have to go in the global map, as it may have
+;;; to coexist with a lot of different major modes.
+
+(setq vc-prefix-map (lookup-key global-map "\C-xv"))
+(if (not (keymapp vc-prefix-map))
+    (progn
+      (setq vc-prefix-map (make-sparse-keymap))
+      (define-key global-map "\C-xv" vc-prefix-map)
+      (define-key vc-prefix-map "a" 'vc-update-change-log)
+      (define-key vc-prefix-map "c" 'vc-cancel-version)
+      (define-key vc-prefix-map "d" 'vc-diff)
+      (define-key vc-prefix-map "h" 'vc-insert-headers)
+      (define-key vc-prefix-map "i" 'vc-register)
+      (define-key vc-prefix-map "l" 'vc-print-log)
+      (define-key vc-prefix-map "r" 'vc-retrieve-snapshot)
+      (define-key vc-prefix-map "s" 'vc-create-snapshot)
+      (define-key vc-prefix-map "u" 'vc-revert-buffer)
+      (define-key vc-prefix-map "v" 'vc-next-action)
+      (define-key vc-prefix-map "=" 'vc-directory)
+      ))
+
+(autoload 'vc-update-change-log "vc.el" nil t)
+(autoload 'vc-cancel-version "vc.el" nil t)
+(autoload 'vc-diff "vc.el" nil t)
+(autoload 'vc-insert-headers "vc.el" nil t)
+(autoload 'vc-register "vc.el" nil t)
+(autoload 'vc-print-log "vc.el" nil t)
+(autoload 'vc-retrieve-snapshot "vc.el" nil t)
+(autoload 'vc-creat-snapshot "vc.el" nil t)
+(autoload 'vc-directory "vc.el" nil t)
+(autoload 'vc-revert-buffer "vc.el" nil t)
+(autoload 'vc-next-action "vc.el" nil t)
+
+(provide 'vc-hooks)
+
+;;; vc-hooks.el ends here
diff --git a/lisp/vc.el b/lisp/vc.el
new file mode 100644
index 0000000000..4c50545035
--- /dev/null
+++ b/lisp/vc.el
@@ -0,0 +1,1567 @@
+;;; vc.el --- drive a version-control system from within Emacs
+
+;; Copyright (C) 1992 Free Software Foundation, Inc.
+
+;; Author: Eric S. Raymond <[email protected]>
+;; Version: 4.0
+
+;;	$Id: vc.el,v 1.58 1992/07/31 07:17:21 esr Exp $	
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 2, or (at your option)
+;; any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to
+;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+;;; Commentary:
+
+;; This was designed and implemented by Eric Raymond <[email protected]>.
+;; Paul Eggert <[email protected]>, Sebastian Kremer <[email protected]>,
+;; and Richard Stallman contributed valuable criticism, support, and testing.
+;;
+;; Supported version-control systems presently include SCCS and RCS;
+;; your RCS version should be 5.6.2 or later for proper operation of
+;; the lock-breaking code.
+;;
+;; The RCS code assumes strict locking.  You can support the RCS -x option
+;; by adding pairs to the vc-master-templates list.
+;;
+;; Proper function of the SCCS diff commands requires the shellscript vcdiff
+;; to be installed somewhere on Emacs's path for executables.
+;;
+;; This code depends on call-process passing back the subprocess exit
+;; status.  Thus, you need Emacs 18.58 or later to run it.
+;;
+;; The vc code maintains some internal state in order to reduce expensive
+;; version-control operations to a minimum.  Some names are only computed
+;; once. If you perform version control operations with RCS/SCCS/CVS while
+;; vc's back is turned, or move/rename master files while vc is running,
+;; vc may get seriously confused.  Don't do these things!
+;;
+;; Developer's notes on some concurrency issues are included at the end of
+;; the file.
+
+;;; Code:
+
+(require 'vc-hooks)
+
+;; General customization
+
+(defvar vc-default-back-end nil
+  "*Back-end actually used by this interface; may be SCCS or RCS.
+The value is only computed when needed to avoid an expensive search.")
+(defvar vc-diff-options '("-a" "-c1")
+  "*The command/flags list to be used in constructing diff commands.")
+(defvar vc-suppress-confirm nil
+  "*If non-nil, reat user as expert; suppress yes-no prompts on some things.")
+(defvar vc-keep-workfiles t
+  "*If non-nil, don't delete working files after registering changes.")
+(defvar vc-initial-comment nil
+  "*Prompt for initial comment when a file is registered.")
+(defvar vc-command-messages nil
+  "*Display run messages from back-end commands.")
+(defvar vc-mistrust-permissions 'file-symlink-p
+  "*Don't assume that permissions and ownership track version-control status.")
+
+;; Header-insertion hair
+
+(defvar vc-header-alist
+  '((SCCS "\%W\%") (RCS "\$Id\$"))
+  "*Header keywords to be inserted when vc-insert-header is executed.")
+(defconst vc-static-header-alist
+  '(("\\.c$" .
+     "\n#ifndef lint\nstatic char vcid[] = \"\%s\";\n#endif /* lint */\n"))
+  "*Associate static header string templates with file types.  A \%s in the
+template is replaced with the first string associated with the file's
+verson-control type in vc-header-strings.")
+(defvar vc-comment-alist
+  '((nroff-mode ".\\\"" ""))
+  "*Special comment delimiters to be used in generating vc headers only.
+Add an entry in this list if you need to override the normal comment-start
+and comment-end variables.  This will only be necessary if the mode language
+is sensitive to blank lines.")
+
+;; Variables the user doesn't need to know about.
+(defvar vc-log-entry-mode nil)
+(defvar vc-log-operation nil)
+
+(defconst vc-name-assoc-file "VC-names")
+
+(defmacro vc-error-occurred (&rest body)
+  (list 'condition-case nil (cons 'progn (append body '(nil))) '(error t)))
+
+;; File property caching
+
+(defun vc-file-clearprops (file)
+  ;; clear all properties of a given file
+  (setplist (intern file vc-file-prop-obarray) nil))
+
+;; Random helper functions
+
+(defun vc-name (file)
+  "Return the master name of a file, nil if it is not registered"
+  (or (vc-file-getprop file 'vc-name)
+      (vc-file-setprop file 'vc-name
+		       (let ((name-and-type (vc-registered file)))
+			 (and name-and-type (car name-and-type))))))
+
+(defvar vc-binary-assoc nil)
+
+(defun vc-find-binary (name)
+  "Look for a command anywhere on the subprocess-command search path."
+  (or (cdr (assoc name vc-binary-assoc))
+      (let ((full nil))
+	(catch 'found
+	  (mapcar
+	   (function (lambda (s)
+	      (if (and s (file-exists-p (setq full (concat s "/" name))))
+		  (throw 'found nil))))
+	  exec-path))
+	(if full
+	    (setq vc-binary-assoc (cons (cons name full) vc-binary-assoc)))
+	full)))
+
+(defun vc-do-command (okstatus command file &rest flags)
+  "Execute a version-control command, notifying user and checking for errors.
+The command is successful if its exit status does not exceed OKSTATUS.
+Output from COMMAND goes to buffer *vc*.  The last argument of the command is
+the master name of FILE; this is appended to an optional list of FLAGS."
+  (setq file (expand-file-name file))
+  (if vc-command-messages
+      (message (format "Running %s on %s..." command file)))
+  (let ((obuf (current-buffer))
+	(squeezed nil)
+	(vc-file (and file (vc-name file)))
+	status)
+    (set-buffer (get-buffer-create "*vc*"))
+    (erase-buffer)
+    (mapcar
+     (function (lambda (s) (and s (setq squeezed (append squeezed (list s))))))
+     flags)
+    (if vc-file
+	(setq squeezed (append squeezed (list vc-file))))
+    (let
+	((default-directory (file-name-directory (or file "./"))))
+      (setq status (apply 'call-process command nil t nil squeezed))
+      )
+    (goto-char (point-max))
+    (previous-line 1)
+    (if (or (not (integerp status)) (< okstatus status))
+	(progn
+	  (previous-line 1)
+	  (print (cons command squeezed))
+	  (next-line 1)
+	  (pop-to-buffer "*vc*")
+	  (vc-shrink-to-fit)
+	  (goto-char (point-min))
+	  (error (format "Running %s...FAILED (%s)" command
+			 (if (integerp status)
+			     (format "status %d" status)
+			   status)))
+	  )
+      (if vc-command-messages
+	  (message (format "Running %s...OK" command)))
+      )
+    (set-buffer obuf)
+    status)
+  )
+
+(defun vc-revert-buffer1 (&optional arg no-confirm)
+  ;; This code was shamelessly lifted from Sebastian Kremer's rcs.el mode.
+  ;; Revert buffer, try to keep point where user expects it in spite
+  ;; of changes because of expanded version-control key words.
+  ;; This is quite important since otherwise typeahead won't work as expected.
+  (interactive "P")
+  (widen)
+  (let* ((opoint (point))
+	 (osize (buffer-size))
+	 diff
+	 (context 100)
+	 (ostring (buffer-substring (point)
+				    (min (point-max)
+					 (+ (point) context))))
+	 (l (length ostring)))
+    (revert-buffer arg no-confirm)
+    (setq diff (- osize (buffer-size)))
+    (if (< diff 0) (setq diff (- diff)))
+    (goto-char opoint)
+    (cond ((equal "" ostring)
+	   (goto-char (point-max)))
+	  ((or (search-forward ostring nil t)
+	       ;; Can't use search-backward since the match may continue
+	       ;; after point.
+	       (progn (goto-char (- (point) diff l))
+		      ;; goto-char doesn't signal an error at
+		      ;; beginning of buffer like backward-char would
+		      (search-forward ostring nil t)))
+	   ;; to beginning of OSTRING
+	   (backward-char l)))))
+
+(defun vc-buffer-sync ()
+  ;; Make sure the current buffer and its working file are in sync
+  (if (and (buffer-modified-p)
+	   (or
+	    vc-suppress-confirm
+	    (y-or-n-p (format "%s has been modified.  Write it out? "
+			      (buffer-name)))))
+      (save-buffer)))
+
+(defun vc-workfile-unchanged-p (file)
+  ;; Has the given workfile changed since last checkout?
+  (let ((checkout-time (vc-file-getprop file 'vc-checkout-time))
+	(lastmod (nth 5 (file-attributes file))))
+    (if checkout-time
+     (equal lastmod checkout-time)
+     (if (zerop (vc-backend-diff file nil))
+	 (progn
+	   (vc-file-setprop file 'vc-checkout-time lastmod)
+	   t)
+       (progn
+	   (vc-file-setprop file 'vc-checkout-time '(0 . 0))
+	   nil
+	 ))
+     )))
+
+;; Here's the major entry point
+
+(defun vc-next-action (verbose)
+  "Do the next logical checkin or checkout operation on the current file.
+   If the file is not already registered, this registers it for version
+control and then retrieves a writeable, locked copy for editing.
+   If the file is registered and not locked by anyone, this checks out
+a writeable and locked file ready for editing.
+   If the file is checked out and locked by the calling user, this
+first checks to see if the file has changed since checkout.  If not,
+it performs a revert.
+   If the file has been changed, this pops up a buffer for creation of
+a log message; when the message has been entered, it checks in the
+resulting changes along with the log message as change commentary.  If
+the variable vc-keep-workfiles is non-nil (which is its default), a
+read-only copy of the changed file is left in place afterwards.
+   If the file is registered and locked by someone else, you are given
+the option to steal the lock."
+  (interactive "P")
+  (if buffer-file-name
+      (let
+	  (do-update owner version
+		     (file buffer-file-name)
+		     (vc-file (vc-name buffer-file-name))
+		     (err-msg nil)
+		     owner)
+
+	(cond
+
+	 ;; if there is no master file corresponding, create one
+	 ((not vc-file)
+	  (vc-register verbose)
+	  (vc-next-action verbose))
+
+	 ;; if there is no lock on the file, assert one and get it
+	 ((not (setq owner (vc-locking-user file)))
+	  (vc-checkout file t))
+
+	 ;; a checked-out version exists, but the user may not own the lock
+	 ((not (string-equal owner (user-login-name)))
+	  (vc-steal-lock
+	   file
+	   (and verbose (read-string "Version to steal: "))
+	   owner))
+
+	 ;; OK, user owns the lock on the file
+	 (t (progn
+
+	      ;; give luser a chance to save before checking in.
+	      (vc-buffer-sync)
+
+	      ;; revert if file is unchanged
+	      (if (vc-workfile-unchanged-p file)
+		  (progn
+		    (vc-backend-revert file)
+		    (vc-resynch-window file t))
+
+		;; user may want to set nonstandard parameters
+		(if verbose
+		    (setq version (read-string "New version level: ")))
+
+		;; OK, let's do the checkin
+		(vc-checkin file version))))))
+    (error "There is no file associated with buffer %s" (buffer-name))))
+
+;;; These functions help the vc-next-action entry point
+
+(defun vc-register (&optional override)
+  "Register the current file into your version-control system."
+  (interactive "P")
+  (if (vc-name buffer-file-name)
+      (error "This file is already registered."))
+  (vc-buffer-sync)
+  (vc-admin
+   buffer-file-name
+   (and override (read-string "Initial version level: ")))
+  )
+
+(defun vc-resynch-window (file &optional keep)
+  ;; If the given file is in the current buffer,
+  ;; either revert on it so we see expanded keyworks,
+  ;; or unvisit it (depending on vc-keep-workfiles)
+  (and (string= buffer-file-name file)
+       (if keep
+	   (progn
+	     (vc-revert-buffer1 nil t)
+	     (vc-mode-line buffer-file-name))
+	 (progn
+	   (delete-window)
+	   (kill-buffer (current-buffer))))))
+
+
+(defun vc-admin (file rev)
+  "Checks a file into your version-control system.
+FILE is the unmodified name of the file.  REV should be the base version
+level to check it in under."
+  (if vc-initial-comment
+      (progn
+	(pop-to-buffer (get-buffer-create "*VC-log*"))
+	(vc-log-mode)
+	(narrow-to-region (point-max) (point-max))
+	(vc-mode-line file (file-name-nondirectory file))
+	(setq vc-log-operation 'vc-backend-admin)
+	(setq vc-log-file file)
+	(setq vc-log-version rev)
+	(message "Enter initial comment.  Type C-c C-c when done."))
+    (progn
+      (vc-backend-admin file rev)
+      (vc-resynch-window file vc-keep-workfiles))))
+
+(defun vc-steal-lock (file rev &optional owner)
+  "Steal the lock on the current workfile."
+  (interactive)
+  (if (not owner)
+      (setq owner (vc-locking-user file)))
+  (if (not (y-or-n-p (format "Take the lock on %s:%s from %s?" file rev owner)))
+      (error "Steal cancelled."))
+  (pop-to-buffer (get-buffer-create "*VC-log*"))
+  (vc-log-mode)
+  (narrow-to-region (point-max) (point-max))
+  (insert
+   (format "To: %s\n\nI stole the lock on %s:%s, " owner file rev)
+   (current-time-string)
+   "\n")
+  (vc-mode-line file (file-name-nondirectory file))
+  (setq vc-log-operation 'vc-finish-steal)
+  (setq vc-log-file file)
+  (setq vc-log-version rev)
+  (message "Please explain why you stole the lock.  Type C-c C-c when done.")
+  )
+
+(defun vc-finish-steal (file version)
+  ;; Actually do the lock acquisition; send the former owner a notification
+  (vc-backend-steal file version)
+  (require 'sendmail)	;; (send-mail) isn't on the standard autoload list.
+  (mail-send)
+  (vc-resynch-window file t)
+  )
+
+(defun vc-checkout (file &optional writeable)
+  "Retrieve a copy of the latest version of the given file."
+  (vc-backend-checkout file writeable)
+  (if (string-equal file buffer-file-name)
+      (vc-resynch-window file t))
+  )
+
+(defun vc-checkin (file &optional rev comment)
+  "Check in the file specified by FILE.
+The optional argument REV may be a string specifying the new version level
+(if nil increment the current level).  The file is either retained with write
+permissions zeroed, or deleted (according to the value of vc-keep-workfiles).
+COMMENT is a comment string; if omitted, a buffer is
+popped up to accept a comment."
+  (pop-to-buffer (get-buffer-create "*VC-log*"))
+  (vc-log-mode)
+  (narrow-to-region (point-max) (point-max))
+  (vc-mode-line file (file-name-nondirectory file))
+  (setq vc-log-operation 'vc-backend-checkin)
+  (setq vc-log-file file)
+  (setq vc-log-version rev)
+  (message "Enter log message.  Type C-c C-c when done.")
+  (if comment
+      (progn
+	(insert comment)
+	(vc-finish-logentry))))
+
+(defun vc-finish-logentry ()
+  "Complete the operation implied by the current log entry."
+  (interactive)
+  (goto-char (point-max))
+  (if (not (bolp)) (newline))
+  ;; delimit current page
+  (save-excursion
+    (widen)
+    (goto-char (point-max))
+    (if (and (not (bobp)) (not (= (char-after (1- (point))) ?\f)))
+	(insert-char ?\f 1)))
+  (if (not (bobp))
+      (forward-char -1))
+  (mark-page)
+  ;; Check for errors
+  (vc-backend-logentry-check vc-log-file)
+  ;; OK, do it to it
+  (if vc-log-operation
+      (funcall vc-log-operation 
+	       vc-log-file
+	       vc-log-version
+	       (buffer-substring (region-beginning) (1- (region-end))))
+    (error "No log operation is pending."))
+  ;; Return to "parent" buffer of this checkin and remove checkin window
+  (pop-to-buffer (get-file-buffer vc-log-file))
+  (delete-window (get-buffer-window "*VC-log*"))
+  (bury-buffer "*VC-log*")
+  ;; Now make sure we see the expanded headers
+  (vc-resynch-window buffer-file-name vc-keep-workfiles)
+  )
+
+;; Code for access to the comment ring
+
+(defun vc-next-comment ()
+  "Fill the log buffer with the next message in the msg ring."
+  (interactive)
+  (widen)
+  (forward-page)
+  (if (= (point) (point-max))
+      (goto-char (point-min)))
+  (mark-page)
+  (narrow-to-page))
+
+(defun vc-previous-comment ()
+  "Fill the log buffer with the previous message in the msg ring."
+  (interactive)
+  (widen)
+  (if (= (point) (point-min))
+      (goto-char (point-max)))
+  (backward-page)
+  (mark-page)
+  (narrow-to-page))
+
+(defun vc-comment-search-backward (regexp)
+  "Fill the log buffer with the last message in the msg ring matching REGEXP."
+  (interactive "sSearch backward for: ")
+  (widen)
+  (if (= (point) (point-min))
+      (goto-char (point-max)))
+  (re-search-backward regexp nil t)
+  (mark-page)
+  (narrow-to-page))
+
+(defun vc-comment-search-forward (regexp)
+  "Fill the log buffer with the next message in the msg ring matching REGEXP."
+  (interactive "sSearch forward for: ")
+  (widen)
+  (if (= (point) (point-min))
+      (goto-char (point-max)))
+  (re-search-forward regexp nil t)
+  (mark-page)
+  (narrow-to-page))
+
+;; Additional entry points for examining version histories
+
+(defun vc-diff (historic)
+  "Display diffs between file versions."
+  (interactive "P")
+  (if historic
+      (call-interactively 'vc-version-diff)
+    (let ((old
+	   (and
+	    current-prefix-arg
+	    (read-string "Version to compare against: ")))
+	  (file buffer-file-name)
+	  unchanged)
+      (vc-buffer-sync)
+      (setq unchanged (vc-workfile-unchanged-p buffer-file-name))
+      (if unchanged
+	  (message (format "No changes to %s since latest version." file))
+	(pop-to-buffer "*vc*")
+	(vc-backend-diff file nil)
+	(goto-char (point-min))
+	)
+      (not unchanged)
+      )
+    )
+  )
+
+(defun vc-version-diff (file rel1 rel2)
+  "For FILE, report diffs between two stored versions REL1 and REL2 of it.
+If FILE is a directory, generate diffs between versions for all registered
+files in or below it."
+  (interactive "FFile or directory: \nsOlder version: \nsNewer version: ")
+  (if (string-equal rel1 "") (setq rel1 nil))
+  (if (string-equal rel2 "") (setq rel2 nil))
+  (if (file-directory-p file)
+      (progn
+	(set-buffer (get-buffer-create "*vc-status*"))
+	(erase-buffer)
+	(insert "Diffs between " rel1 " and " rel2 ":\n\n")
+	(set-buffer (get-buffer-create "*vc*"))
+	(vc-file-tree-walk
+	 (function (lambda (f)
+		     (and
+		      (not (file-directory-p f))
+		      (vc-name f)
+		      (vc-backend-diff f rel1 rel2))
+		     (append-to-buffer "*vc-status*" (point-min) (point-max))
+		     ))
+	 default-directory)
+	(pop-to-buffer "*vc-status*")
+	(insert "\nEnd of diffs.\n")
+	(goto-char (point-min))
+	(set-buffer-modified-p nil)
+	)
+    (progn
+      (vc-backend-diff file rel1 rel2)
+      (goto-char (point-min))
+      (if (equal (point-min) (point-max))
+	  (message (format "No changes to %s between %s and %s." file rel1 rel2))
+	(pop-to-buffer "*vc*")
+	(goto-char (point-min))
+	)
+      )
+    )
+  )
+
+;; Header-insertion code
+
+(defun vc-insert-headers ()
+  "Insert headers in a file for use with your version-control system.
+Headers desired are inserted at the start of the buffer, and are pulled from
+the variable vc-header-strings"
+  (interactive)
+  (save-excursion
+    (save-restriction
+      (widen)
+      (if (or (not (vc-check-headers))
+	      (y-or-n-p "Version headers already exist.  Insert another set?"))
+	  (progn
+	    (let* ((delims (cdr (assq major-mode vc-comment-alist)))
+		   (comment-start-vc (or (car delims) comment-start "#"))
+		   (comment-end-vc (or (car (cdr delims)) comment-end ""))
+		   (hdstrings (cdr (assoc (vc-backend-deduce (buffer-file-name)) vc-header-alist))))
+	      (mapcar (function (lambda (s)
+				  (insert comment-start-vc "\t" s "\t"
+					  comment-end-vc "\n")))
+		      hdstrings)
+	      (if vc-static-header-alist
+		  (mapcar (function (lambda (f)
+				      (if (string-match (car f) buffer-file-name)
+					  (insert (format (cdr f) (car hdstrings))))))
+			  vc-static-header-alist))
+	      )
+	    )))))
+
+;; Status-checking functions
+
+(defun vc-directory (verbose)
+  "Show version-control status of all files under the current directory."
+  (interactive "P")
+  (let ((dir (substring default-directory 0 (1- (length default-directory))))
+	nonempty)
+    (save-excursion
+      (set-buffer (get-buffer-create "*vc-status*"))
+      (erase-buffer)
+      (vc-file-tree-walk
+       (function (lambda (f)
+		   (if (vc-registered f)
+		       (let ((user (vc-locking-user f)))
+			 (if (or user verbose)
+			     (insert (format
+				      "%s	%s\n"
+				      (concat user) f)))))))
+       dir)
+      (setq nonempty (not (zerop (buffer-size)))))
+    (if nonempty
+	(progn
+	  (pop-to-buffer "*vc-status*" t)
+	  (vc-shrink-to-fit)
+	  (goto-char (point-min)))
+      (message "No files are currently registered under %s" dir))
+    ))
+
+;; Named-configuration support for SCCS
+
+(defun vc-add-triple (name file rev)
+  (save-excursion
+    (find-file (concat (vc-backend-subdirectory-name file) "/" vc-name-assoc-file))
+    (goto-char (point-max))
+    (insert name "\t:\t" file "\t" rev "\n")
+    (basic-save-buffer)
+    (kill-buffer (current-buffer))
+    ))
+
+(defun vc-record-rename (file newname)
+  (save-excursion
+    (find-file (concat (vc-backend-subdirectory-name file) "/" vc-name-assoc-file))
+    (goto-char (point-min))
+    (replace-regexp (concat ":" (regexp-quote file) "$") (concat ":" newname))
+    (basic-save-buffer)
+    (kill-buffer (current-buffer))
+    ))
+
+(defun vc-lookup-triple (file name)
+  (or
+   name
+   (let ((firstchar (aref name 0)))
+     (and (>= firstchar ?0) (<= firstchar ?9) name))
+   (car (vc-master-info
+    (concat (vc-backend-subdirectory-name file) "/" vc-name-assoc-file)
+    (list (concat name "\t:\t" file "\t\\(.+\\)"))))
+   ))
+
+;; Named-configuration entry points
+
+(defun vc-quiescent-p ()
+  ;; Is the current directory ready to be snapshot?
+  (let ((dir (substring default-directory 0 (1- (length default-directory)))))
+    (catch 'quiet
+      (vc-file-tree-walk
+       (function (lambda (f)
+		   (if (and (vc-registered f) (vc-locking-user f))
+		       (throw 'quiet nil))))
+       dir)
+      t)))
+
+(defun vc-create-snapshot (name)
+  "Make a snapshot called NAME.
+The snapshot is made from all registered files at or below the current
+directory.  For each file, the version level of its latest
+version becomes part of the named configuration."
+  (interactive "sNew snapshot name: ")
+  (if (not (vc-quiescent-p))
+      (error "Can't make a snapshot, locked files are in the way.")
+    (vc-file-tree-walk
+     (function (lambda (f) (and
+		   (not (file-directory-p f))
+		   (vc-name f)
+		   (vc-backend-assign-name f name))))
+     default-directory)
+    ))
+
+(defun vc-retrieve-snapshot (name)
+  "Retrieve the snapshot called NAME.
+This function fails if any files are locked at or below the current directory
+Otherwise, all registered files are checked out (unlocked) at their version
+levels in the snapshot."
+  (interactive "sSnapshot name to retrieve: ")
+  (if (not (vc-quiescent-p))
+      (error "Can't retrieve a snapshot, locked files are in the way.")
+    (vc-file-tree-walk
+     (function (lambda (f) (and
+		   (not (file-directory-p f))
+		   (vc-name f)
+		   (vc-error-occurred (vc-backend-checkout f nil name)))))
+     default-directory)
+    ))
+
+;; Miscellaneous other entry points
+
+(defun vc-print-log ()
+  "List the change log of the current buffer in a window."
+  (interactive)
+  (if (and buffer-file-name (vc-name buffer-file-name))
+      (progn
+	(vc-backend-print-log buffer-file-name)
+	(pop-to-buffer (get-buffer-create "*vc*"))
+	(goto-char (point-min))
+	)
+    (error "There is no version-control master associated with this buffer")
+    )
+  )
+
+(defun vc-revert-buffer ()
+  "Revert the current buffer's file back to the latest version."
+  (interactive)
+  (let ((file buffer-file-name)
+	(obuf (current-buffer)) (changed (vc-diff nil)))
+    (if (and changed (or vc-suppress-confirm (not (y-or-n-p "Discard changes? "))))
+	(progn
+	  (delete-window)
+	  (error "Revert cancelled."))
+      (set-buffer obuf))
+    (if changed
+	(delete-window))
+    (vc-backend-revert file)
+    (vc-resynch-window file t)
+    )
+  )
+
+(defun vc-cancel-version (norevert)
+  "Undo your latest checkin."
+  (interactive "P")
+  (let ((target (vc-your-latest-version (buffer-file-name))))
+    (if (null target)
+	(error "You didn't check in the last change."))
+    (and (y-or-n-p (format "Remove version %s from master? " target))
+      (vc-backend-uncheck (buffer-file-name) target)))
+    (if norevert
+	(vc-mode-line (buffer-file-name))
+	(vc-checkout (buffer-file-name) nil))
+  )
+
+(defun vc-rename-file (old new)
+  "Rename a file, taking its master files with it."
+  (interactive "fOld name: \nFNew name: ")
+  (let ((oldbuf (get-file-buffer old)))
+    (if (buffer-modified-p oldbuf)
+	(error "Please save files before moving them."))
+    (if (get-file-buffer new)
+	(error "Already editing new file name."))
+    (let ((oldmaster (vc-name old)))
+      (if oldmaster
+	(if (vc-locking-user old)
+	    (error "Please check in files before moving them."))
+	(if (or (file-symlink-p oldmaster)
+		(file-symlink-p (vc-backend-subdirectory-name file)))
+	    (error "This is not a safe thing to do in the presence of symbolic links."))
+	(rename-file oldmaster (vc-name new)))
+      (if (or (not oldmaster) (file-exists-p old))
+	  (rename-file old new)))
+; ?? Renaming a file might change its contents due to keyword expansion.
+; We should really check out a new copy if the old copy was precisely equal
+; to some checked in version.  However, testing for this is tricky....
+    (if oldbuf
+	(save-excursion
+	  (set-buffer oldbuf)
+	  (set-visited-file-name new)
+	  (set-buffer-modified-p nil))))
+  (vc-backend-dispatch file
+		       (vc-record-rename old new)
+		       nil)
+  )
+
+(defun vc-update-change-log ()
+  "Find change log file and add entries from recent RCS logs."
+  (interactive)
+    (find-file-other-window "ChangeLog")
+    (vc-buffer-sync)
+    (or (eq major-mode 'indented-text-mode)
+	(progn
+	  (indented-text-mode)
+	  (setq left-margin 8)
+	  (setq fill-column 74)))
+    (auto-fill-mode 1)
+    (undo-boundary)
+    (goto-char (point-min))
+    (message "Computing change log entries...")
+    (shell-command-on-region (point) (point) "rcs2log" t)
+    (message "Computing change log entries... done"))
+
+;; Functions for querying the master and lock files.
+
+(defun match-substring (bn)
+  (buffer-substring (match-beginning bn) (match-end bn)))
+
+(defun vc-parse-buffer (patterns &optional file properties)
+  ;; Use PATTERNS to parse information out of the current buffer
+  ;; by matching each regular expression in the list and returning \\1.
+  ;; If a regexp has two tag brackets, assume the second is a date
+  ;; field and we want the most recent entry matching the template.
+  ;; If FILE and PROPERTIES are given, the latter must be a list of
+  ;; properties of the same length as PATTERNS; each property is assigned 
+  ;; the corresponding value.
+  (mapcar (function (lambda (p)
+	     (goto-char (point-min))
+	     (if (string-match "\\\\(.*\\\\(" p)
+		 (let ((latest-date "") (latest-val))
+		   (while (re-search-forward p nil t)
+		     (let ((date (match-substring 2)))
+		       (if (string< latest-date date)
+			   (progn
+			     (setq latest-date date)
+			     (setq latest-val
+				   (match-substring 1))))))
+		   latest-val))
+	     (prog1
+		 (and (re-search-forward p nil t)
+		      (let ((value (match-substring 1)))
+			(if file
+			    (vc-file-setprop file (car properties) value))
+			value))
+	       (setq properties (cdr properties)))))
+	  patterns)
+  )
+
+(defun vc-master-info (file fields &optional rfile properties)
+  ;; Search for information in a master file.
+  (if (and file (file-exists-p file))
+      (save-excursion
+	(let ((buf))
+	  (setq buf (create-file-buffer file))
+	  (set-buffer buf))
+	(erase-buffer)
+	(insert-file-contents file nil)
+	(set-buffer-modified-p nil)
+	(auto-save-mode nil)
+	(prog1
+	    (vc-parse-buffer fields rfile properties)
+	  (kill-buffer (current-buffer)))
+	)
+    (if rfile
+	(mapcar
+	 (function (lambda (p) (vc-file-setprop rfile p nil)))
+	 properties))
+    )
+  )
+
+(defun vc-log-info (command file patterns &optional properties)
+  ;; Search for information in log program output
+  (if (and file (file-exists-p file))
+      (save-excursion
+	(let ((buf))
+	  (setq buf (get-buffer-create "*vc*"))
+	  (set-buffer buf))
+	(apply 'vc-do-command 0 command file nil)
+	(set-buffer-modified-p nil)
+	(prog1
+	    (vc-parse-buffer patterns file properties)
+	  (kill-buffer (current-buffer))
+	  )
+	)
+    (if file
+	(mapcar
+	 (function (lambda (p) (vc-file-setprop file p nil)))
+	 properties))
+    )
+  )
+
+(defun vc-locking-user (file)
+  "Return the name of the person currently holding a lock on FILE.
+Return nil if there is no such person."
+  (if (or (not vc-keep-workfiles)
+	  (eq vc-mistrust-permissions 't)
+	  (and vc-mistrust-permissions
+	       (funcall vc-mistrust-permissions (vc-backend-subdirectory-name file))))
+      (vc-true-locking-user file)
+    ;; This implementation assumes that any file which is under version
+    ;; control and has -rw-r--r-- is locked by its owner.  This is true
+    ;; for both RCS and SCCS, which keep unlocked files at -r--r--r--.
+    ;; We have to be careful not to exclude files with execute bits on;
+    ;; scripts can be under version control too.  The advantage of this
+    ;; hack is that calls to the very expensive vc-fetch-properties
+    ;; function only have to be made if (a) the file is locked by someone
+    ;; other than the current user, or (b) some untoward manipulation
+    ;; behind vc's back has twiddled the `group' or `other' write bits.
+    (let ((attributes (file-attributes file)))
+      (cond ((string-match ".r-.r-.r-." (nth 8 attributes))
+	     nil)
+	    ((and (= (nth 2 attributes) (user-uid))
+		  (string-match ".rw.r-.r-." (nth 8 attributes)))
+	     (user-login-name))
+	    (t
+	     (vc-true-locking-user file))))))
+
+(defun vc-true-locking-user (file)
+  ;; The slow but reliable version
+  (vc-fetch-properties file)
+  (vc-file-getprop file 'vc-locking-user))
+
+(defun vc-latest-version (file)
+  ;; Return version level of the latest version of FILE
+  (vc-fetch-properties file)
+  (vc-file-getprop file 'vc-latest-version))
+
+(defun vc-your-latest-version (file)
+  ;; Return version level of the latest version of FILE checked in by you
+  (vc-fetch-properties file)
+  (vc-file-getprop file 'vc-your-latest-version))
+
+;; Collect back-end-dependent stuff here
+;;
+;; Everything eventually funnels through these functions.  To implement
+;; support for a new version-control system, add another branch to the
+;; vc-backend-dispatch macro (in vc-hooks.el) and fill it in in each call.
+
+(defmacro vc-backend-dispatch (f s r)
+  "Execute FORM1 or FORM2 depending on whether we're using SCCS or RCS."
+  (list 'let (list (list 'type (list 'vc-backend-deduce f)))
+	(list 'cond
+	      (list (list 'eq 'type (quote 'SCCS)) s)	;; SCCS
+	      (list (list 'eq 'type (quote 'RCS)) r)	;; RCS
+	      )))
+
+(defun vc-lock-file (file)
+  ;; Generate lock file name corresponding to FILE
+  (let ((master (vc-name file)))
+    (and
+     master
+     (string-match "\\(.*/\\)s\\.\\(.*\\)" master)
+     (concat
+      (substring master (match-beginning 1) (match-end 1))
+      "p."
+      (substring master (match-beginning 2) (match-end 2))))))
+
+
+(defun vc-fetch-properties (file)
+  ;; Re-fetch all properties associated with the given file.
+  ;; Currently these properties are:
+  ;;	vc-locking-user
+  ;;	vc-locked-version
+  ;;    vc-latest-version
+  ;;    vc-your-latest-version
+  (vc-backend-dispatch
+   file
+   ;; SCCS
+   (progn
+     (vc-master-info (vc-lock-file file)
+		     (list
+		      "^[^ ]+ [^ ]+ \\([^ ]+\\)"
+		      "^\\([^ ]+\\)")
+		     file
+		     '(vc-locking-user vc-locked-version))
+     (vc-master-info (vc-name file)
+		  (list
+		   "^\001d D \\([^ ]+\\)"
+		   (concat "^\001d D \\([^ ]+\\) .* " 
+			   (regexp-quote (user-login-name)) " ")
+		   )
+		  file
+		  '(vc-latest-version vc-your-latest-version))
+     )
+   ;; RCS
+   (vc-log-info "rlog" file
+		(list
+		 "^locks: strict\n\t\\([^:]+\\)"
+		 "^locks: strict\n\t[^:]+: \\(.+\\)"
+		 "^revision[\t ]+\\([0-9.]+\\).*\ndate: \\([ /0-9:]+\\);"
+		 (concat
+		  "^revision[\t ]+\\([0-9.]+\\).*locked by: "
+		  (regexp-quote (user-login-name))
+		  ";\ndate: \\([ /0-9:]+\\);"))
+		'(vc-locking-user vc-locked-version
+				  vc-latest-version vc-your-latest-version))
+   ))
+
+(defun vc-backend-subdirectory-name (&optional file)
+  ;; Where the master and lock files for the current directory are kept
+  (symbol-name
+   (or
+    (and file (vc-backend-deduce file))
+    vc-default-back-end
+    (setq vc-default-back-end (if (vc-find-binary "rcs") 'RCS 'SCCS)))))
+
+(defun vc-backend-admin (file &optional rev comment)
+  ;; Register a file into the version-control system
+  ;; Automatically retrieves a read-only version of the file with
+  ;; keywords expanded if vc-keep-workfiles is non-nil, otherwise
+  ;; it deletes the workfile.
+  (vc-file-clearprops file)
+  (or vc-default-back-end
+      (setq vc-default-back-end (if (vc-find-binary "rcs") 'RCS 'SCCS)))
+  (message "Registering %s..." file)
+  (let ((backend
+	 (cond
+	  ((file-exists-p (vc-backend-subdirectory-name)) vc-default-back-end)
+	  ((file-exists-p "RCS") 'RCS)
+	  ((file-exists-p "SCCS") 'SCCS)
+	  (t vc-default-back-end))))
+    (cond ((eq backend 'SCCS)
+	   (vc-do-command 0 "admin" file	;; SCCS
+			  (and rev (concat "-r" rev))
+			  "-fb"
+			  (concat "-i" file)
+			  (and comment (concat "-y" comment))
+			  (format
+			   (car (rassq 'SCCS vc-master-templates))
+			   (or (file-name-directory file) "")
+			   (file-name-nondirectory file)))
+	   (delete-file file)
+	   (if vc-keep-workfiles
+	       (vc-do-command 0 "get" file)))
+	  ((eq backend 'RCS)
+	   (vc-do-command 0 "ci" file	;; RCS
+			  (concat (if vc-keep-workfiles "-u" "-r") rev)
+			  (and comment (concat "-t-" comment))
+			  file)
+	   )))
+  (message "Registering %s...done" file)
+  )
+
+(defun vc-backend-checkout (file &optional writeable rev)
+  ;; Retrieve a copy of a saved version into a workfile
+  (message "Checking out %s..." file)
+  (vc-backend-dispatch file
+   (progn
+     (vc-do-command 0 "get" file	;; SCCS
+		    (if writeable "-e")
+		    (and rev (concat "-r" (vc-lookup-triple file rev))))
+     )
+   (vc-do-command 0 "co" file	;; RCS
+		  (if writeable "-l")
+		  (and rev (concat "-r" rev)))
+   )
+  (vc-file-setprop file 'vc-checkout-time (nth 5 (file-attributes file)))
+  (message "Checking out %s...done" file)
+  )
+
+(defun vc-backend-logentry-check (file)
+  (vc-backend-dispatch file
+   (if (>= (- (region-end) (region-beginning)) 512)	;; SCCS
+       (progn
+	 (goto-char 512)
+	 (error
+	  "Log must be less than 512 characters.  Point is now at char 512.")))
+   nil)
+  )
+
+(defun vc-backend-checkin (file &optional rev comment)
+  ;; Register changes to FILE as level REV with explanatory COMMENT.
+  ;; Automatically retrieves a read-only version of the file with
+  ;; keywords expanded if vc-keep-workfiles is non-nil, otherwise
+  ;; it deletes the workfile.
+  (message "Checking in %s..." file)
+  (vc-backend-dispatch file
+   (progn
+     (vc-do-command 0 "delta" file
+		    (if rev (concat "-r" rev))
+		    (concat "-y" comment))
+     (if vc-keep-workfiles
+	 (vc-do-command 0 "get" file))
+     )
+   (vc-do-command 0 "ci" file
+		  (concat (if vc-keep-workfiles "-u" "-r") rev)
+		  (concat "-m" comment))
+   )
+  (vc-file-setprop file 'vc-locking-user nil)
+  (message "Checking in %s...done" file)
+  )
+
+(defun vc-backend-revert (file)
+  ;; Revert file to latest checked-in version.
+  (message "Reverting %s..." file)
+  (vc-backend-dispatch
+   file
+   (progn			;; SCCS
+     (vc-do-command 0 "unget" file nil)
+     (vc-do-command 0 "get" file nil))
+   (progn
+     (delete-file file)		;; RCS
+     (vc-do-command 0 "co" file "-u")))
+  (vc-file-setprop file 'vc-locking-user nil)
+  (message "Reverting %s...done" file)
+  )
+
+(defun vc-backend-steal (file &optional rev)
+  ;; Steal the lock on the current workfile.  Needs RCS 5.6.2 or later for -M.
+  (message "Stealing lock on %s..." file)
+  (progn
+    (vc-do-command 0 "unget" file "-n" (if rev (concat "-r" rev)))
+    (vc-do-command 0 "get" file "-g" (if rev (concat "-r" rev)))
+    )
+  (progn
+    (vc-do-command 0 "rcs" file "-M" (concat "-u" rev))
+    (vc-do-command 0 "rcs" file (concat "-l" rev))
+    )
+  (vc-file-setprop file 'vc-locking-user (user-login-name))
+  (message "Stealing lock on %s...done" file)
+  )  
+
+(defun vc-backend-uncheck (file target)
+  ;; Undo the latest checkin.  Note: this code will have to get a lot
+  ;; smarter when we support multiple branches.
+  (message "Removing last change from %s..." file)
+  (vc-backend-dispatch file
+   (vc-do-command 0 "rmdel" file (concat "-r" target))
+   (vc-do-command 0 "rcs" file (concat "-o" target))
+   )
+  (message "Removing last change from %s...done" file)
+  )
+
+(defun vc-backend-print-log (file)
+  ;; Print change log associated with FILE to buffer *vc*.
+  (vc-do-command 0
+		 (vc-backend-dispatch file "prs" "rlog")
+		 file)
+  )
+
+(defun vc-backend-assign-name (file name)
+  ;; Assign to a FILE's latest version a given NAME.
+  (vc-backend-dispatch file
+   (vc-add-triple name file (vc-latest-version file))	;; SCCS
+   (vc-do-command 0 "rcs" file (concat "-n" name ":"))	;; RCS
+   ))
+
+(defun vc-backend-diff (file oldvers &optional newvers)
+  ;; Get a difference report between two versions
+  (apply 'vc-do-command 1
+	 (or (vc-backend-dispatch file "vcdiff" "rcsdiff")
+	     (error (format "File %s is not under version control." file)))
+	 file
+	 (and oldvers (concat "-r" oldvers))
+	 (and newvers (concat "-r" newvers))
+	 vc-diff-options
+  ))
+
+(defun vc-check-headers ()
+  "Check if the current file has any headers in it."
+  (interactive)
+  (save-excursion
+    (goto-char (point-min))
+    (vc-backend-dispatch buffer-file-name
+     (re-search-forward  "%[MIRLBSDHTEGUYFPQCZWA]%" nil t)	;; SCCS
+     (re-search-forward "\\$[A-Za-z\300-\326\330-\366\370-\377]+\\(: [\t -#%-\176\240-\377]*\\)?\\$" nil t)		;; RCS
+     )
+    ))
+
+;; Back-end-dependent stuff ends here.
+
+;; Set up key bindings for use while editing log messages
+
+(defun vc-log-mode ()
+  "Minor mode for driving version-control tools.
+These bindings are added to the global keymap when you enter this mode:
+\\[vc-next-action]		perform next logical version-control operation on current file
+\\[vc-register]			register current file
+\\[vc-toggle-read-only]		like next-action, but won't register files
+\\[vc-insert-headers]		insert version-control headers in current file
+\\[vc-print-log]		display change history of current file
+\\[vc-revert-buffer]		revert buffer to latest version
+\\[vc-cancel-version]		undo latest checkin
+\\[vc-diff]		show diffs between file versions
+\\[vc-directory]		show all files locked by any user in or below .
+\\[vc-update-change-log]		add change log entry from recent checkins
+
+While you are entering a change log message for a version, the following
+additional bindings will be in effect.
+
+\\[vc-finish-logentry]	proceed with check in, ending log message entry
+
+Whenever you do a checkin, your log comment is added to a ring of
+saved comments.  These can be recalled as follows:
+
+\\[vc-next-comment]	replace region with next message in comment ring
+\\[vc-previous-comment]	replace region with previous message in comment ring
+\\[vc-search-comment-reverse]	search backward for regexp in the comment ring
+\\[vc-search-comment-forward]	search backward for regexp in the comment ring
+
+Entry to the change-log submode calls the value of text-mode-hook, then
+the value of vc-log-mode-hook.
+
+Global user options:
+	vc-initial-comment	If non-nil, require user to enter a change
+				comment upon first checkin of the file.
+
+	vc-keep-workfiles	Non-nil value prevents workfiles from being
+				deleted when changes are checked in
+
+        vc-suppress-confirm     Suppresses some confirmation prompts,
+				notably for reversions.
+
+	vc-diff-options         A list consisting of the flags
+				to be used for generating context diffs.
+
+	vc-header-strings	Which keywords to insert when adding headers
+				with \\[vc-insert-headers].  Defaults to
+				'(\"\%\W\%\") under SCCS, '(\"\$Id\$\") under RCS.
+
+	vc-static-header-alist	By default, version headers inserted in C files
+				get stuffed in a static string area so that
+				ident(RCS) or what(SCCS) can see them in the
+				compiled object code.  You can override this
+				by setting this variable to nil, or change
+				the header template by changing it.
+
+	vc-command-messages	if non-nil, display run messages from the
+				actual version-control utilities (this is
+				intended primarily for people hacking vc
+				itself).
+"
+  (interactive)
+  (set-syntax-table text-mode-syntax-table)
+  (use-local-map vc-log-entry-mode)
+  (setq local-abbrev-table text-mode-abbrev-table)
+  (setq major-mode 'vc-log-mode)
+  (setq mode-name "VC-Log")
+  (make-local-variable 'vc-log-file)
+  (make-local-variable 'vc-log-version)
+  (set-buffer-modified-p nil)
+  (setq buffer-file-name nil)
+  (run-hooks 'text-mode-hook 'vc-log-mode-hook)
+)
+
+;; Initialization code, to be done just once at load-time
+(if vc-log-entry-mode
+    nil
+  (setq vc-log-entry-mode (make-sparse-keymap))
+  (define-key vc-log-entry-mode "\M-n" 'vc-next-comment)
+  (define-key vc-log-entry-mode "\M-p" 'vc-previous-comment)
+  (define-key vc-log-entry-mode "\M-r" 'vc-comment-search-backward)
+  (define-key vc-log-entry-mode "\M-s" 'vc-comment-search-forward)
+  (define-key vc-log-entry-mode "\C-c\C-c" 'vc-finish-logentry)
+  )
+
+;;; These things should probably be generally available
+
+(defun vc-shrink-to-fit ()
+  "Shrink a window vertically until it's just large enough to contain its text"
+  (let ((minsize (1+ (count-lines (point-min) (point-max)))))
+    (if (< minsize (window-height))
+	(let ((window-min-height 2))
+	  (shrink-window (- (window-height) minsize))))))
+
+(defun vc-file-tree-walk (func dir &rest args)
+  "Apply a given function to dir and all files underneath it, recursively."
+  (apply 'funcall func dir args)
+  (and (file-directory-p dir)
+       (mapcar
+	(function (lambda (f) (or
+		      (string-equal f ".")
+		      (string-equal f "..")
+		      (file-symlink-p f)	;; Avoid possible loops
+		      (apply 'vc-file-tree-walk
+			     func
+			     (if (= (aref dir (1- (length dir))) ?/)
+				 (concat dir f)
+			       (concat dir "/" f))
+			     args))))
+	(directory-files dir))))
+
+(provide 'vc)
+
+;;; DEVELOPER'S NOTES ON CONCURRENCY PROBLEMS IN THIS CODE
+;;;
+;;; These may be useful to anyone who has to debug or extend the package.
+;;; 
+;;; A fundamental problem in VC is that there are time windows between
+;;; vc-next-action's computations of the file's version-control state and
+;;; the actions that change it.  This is a window open to lossage in a
+;;; multi-user environment; someone else could nip in and change the state
+;;; of the master during it.
+;;; 
+;;; The performance problem is that rlog/prs calls are very expensive; we want
+;;; to avoid them as much as possible.
+;;; 
+;;; ANALYSIS:
+;;; 
+;;; The performance problem, it turns out, simplifies in practice to the
+;;; problem of making vc-locking-user fast.  The two other functions that call
+;;; prs/rlog will not be so commonly used that the slowdown is a problem; one
+;;; makes snapshots, the other deletes the calling user's last change in the
+;;; master.
+;;; 
+;;; The race condition implies that we have to either (a) lock the master
+;;; during the entire execution of vc-next-action, or (b) detect and
+;;; recover from errors resulting from dispatch on an out-of-date state.
+;;; 
+;;; Alternative (a) appears to be unfeasible.  The problem is that we can't
+;;; guarantee that the lock will ever be removed.  Suppose a user starts a
+;;; checkin, the change message buffer pops up, and the user, having wandered
+;;; off to do something else, simply forgets about it?
+;;; 
+;;; Alternative (b), on the other hand, works well with a cheap way to speed up
+;;; vc-locking-user.  Usually, if a file is registered, we can read its locked/
+;;; unlocked state and its current owner from its permissions.
+;;; 
+;;; This shortcut will fail if someone has manually changed the workfile's
+;;; permissions; also if developers are munging the workfile in several
+;;; directories, with symlinks to a master (in this latter case, the
+;;; permissions shortcut will fail to detect a lock asserted from another
+;;; directory).
+;;; 
+;;; Note that these cases correspond exactly to the errors which could happen
+;;; because of a competing checkin/checkout race in between two instances of
+;;; vc-next-action.
+;;; 
+;;; For VC's purposes, a workfile/master pair may have the following states:
+;;; 
+;;; A. Unregistered.  There is a workfile, there is no master.
+;;; 
+;;; B. Registered and not locked by anyone.
+;;; 
+;;; C. Locked by calling user and unchanged.
+;;; 
+;;; D. Locked by the calling user and changed.
+;;; 
+;;; E. Locked by someone other than the calling user.
+;;; 
+;;; This makes for 25 states and 20 error conditions.  Here's the matrix:
+;;; 
+;;; VC's idea of state
+;;;  |
+;;;  V  Actual state   RCS action              SCCS action          Effect
+;;;    A  B  C  D  E
+;;;  A .  1  2  3  4   ci -u -t-          admin -fb -i<file>      initial admin
+;;;  B 5  .  6  7  8   co -l              get -e                  checkout
+;;;  C 9  10 .  11 12  co -u              unget; get              revert
+;;;  D 13 14 15 .  16  ci -u -m<comment>  delta -y<comment>; get  checkin
+;;;  E 17 18 19 20 .   rcs -u -M ; rcs -l unget -n ; get -g       steal lock
+;;; 
+;;; All commands take the master file name as a last argument (not shown).
+;;; 
+;;; In the discussion below, a "self-race" is a pathological situation in
+;;; which VC operations are being attempted simultaneously by two or more
+;;; Emacsen running under the same username.
+;;; 
+;;; The vc-next-action code has the following windows:
+;;; 
+;;; Window P:
+;;;    Between the check for existence of a master file and the call to
+;;; admin/checkin in vc-buffer-admin (apparent state A).  This window may
+;;; never close if the initial-comment feature is on.
+;;; 
+;;; Window Q:
+;;;    Between the call to vc-workfile-unchanged-p in and the immediately
+;;; following revert (apparent state C).
+;;; 
+;;; Window R:
+;;;    Between the call to vc-workfile-unchanged-p in and the following
+;;; checkin (apparent state D).  This window may never close.
+;;; 
+;;; Window S:
+;;;    Between the unlock and the immediately following checkout during a
+;;; revert operation (apparent state C).  Included in window Q.
+;;; 
+;;; Window T:
+;;;    Between vc-locking-user and the following checkout (apparent state B).
+;;; 
+;;; Window U:
+;;;    Between vc-locking-user and the following revert (apparent state C).
+;;; Includes windows Q and S.
+;;; 
+;;; Window V:
+;;;    Between vc-locking-user and the following checkin (apparent state
+;;; D).  This window may never be closed if the user fails to complete the
+;;; checkin message.  Includes window R.
+;;; 
+;;; Window W:
+;;;    Between vc-locking-user and the following steal-lock (apparent
+;;; state E).  This window may never cloce if the user fails to complete
+;;; the steal-lock message.  Includes window X.
+;;; 
+;;; Window X:
+;;;    Between the unlock and the immediately following re-lock during a
+;;; steal-lock operation (apparent state E).  This window may never cloce
+;;; if the user fails to complete the steal-lock message.
+;;; 
+;;; Errors:
+;;; 
+;;; Apparent state A ---
+;;;
+;;; 1. File looked unregistered but is actually registered and not locked.
+;;; 
+;;;    Potential cause: someone else's admin during window P, with
+;;; caller's admin happening before their checkout.
+;;; 
+;;;    RCS: ci will fail with a "no lock set by <user>" message.
+;;;    SCCS: admin will fail with error (ad19).
+;;; 
+;;;    We can let these errors be passed up to the user.
+;;; 
+;;; 2. File looked unregistered but is actually locked by caller, unchanged.
+;;; 
+;;;    Potential cause: self-race during window P.
+;;; 
+;;;    RCS: will revert the file to the last saved version and unlock it.
+;;;    SCCS: will fail with error (ad19).
+;;; 
+;;;    Either of these consequences is acceptable.
+;;; 
+;;; 3. File looked unregistered but is actually locked by caller, changed.
+;;; 
+;;;    Potential cause: self-race during window P.
+;;; 
+;;;    RCS: will register the caller's workfile as a delta with a
+;;; null change comment (the -t- switch will be ignored).
+;;;    SCCS: will fail with error (ad19).
+;;; 
+;;; 4. File looked unregistered but is locked by someone else.
+;;; 
+;;;    Potential cause: someone else's admin during window P, with
+;;; caller's admin happening *after* their checkout.
+;;; 
+;;;    RCS: will fail with a "no lock set by <user>" message.
+;;;    SCCS: will fail with error (ad19).
+;;; 
+;;;    We can let these errors be passed up to the user.
+;;; 
+;;; Apparent state B ---
+;;;
+;;; 5. File looked registered and not locked, but is actually unregistered.
+;;; 
+;;;    Potential cause: master file got nuked during window P.
+;;; 
+;;;    RCS: will fail with "RCS/<file>: No such file or directory"
+;;;    SCCS: will fail with error ut4.
+;;; 
+;;;    We can let these errors be passed up to the user.
+;;; 
+;;; 6. File looked registered and not locked, but is actually locked by the
+;;; calling user and unchanged.
+;;; 
+;;;    Potential cause: self-race during window T.
+;;; 
+;;;    RCS: in the same directory as the previous workfile, co -l will fail
+;;; with "co error: writable foo exists; checkout aborted".  In any other
+;;; directory, checkout will succeed.
+;;;    SCCS: will fail with ge17.
+;;; 
+;;;    Either of these consequences is acceptable.
+;;; 
+;;; 7. File looked registered and not locked, but is actually locked by the
+;;; calling user and changed.
+;;; 
+;;;    As case 6.
+;;; 
+;;; 8. File looked registered and not locked, but is actually locked by another
+;;; user.
+;;; 
+;;;    Potential cause: someone else checks it out during window T.
+;;; 
+;;;    RCS: co error: revision 1.3 already locked by <user>
+;;;    SCCS: fails with ge4 (in directory) or ut7 (outside it).
+;;; 
+;;;    We can let these errors be passed up to the user.
+;;; 
+;;; Apparent state C ---
+;;;
+;;; 9. File looks locked by calling user and unchanged, but is unregistered.
+;;; 
+;;;    As case 5.
+;;; 
+;;; 10. File looks locked by calling user and unchanged, but is actually not
+;;; locked.
+;;; 
+;;;    Potential cause: a self-race in window U, or by the revert's
+;;; landing during window X of some other user's steal-lock or window S
+;;; of another user's revert.
+;;; 
+;;;    RCS: succeeds, refreshing the file from the identical version in
+;;; the master.
+;;;    SCCS: fails with error ut4 (p file nonexistent).
+;;;
+;;;    Either of these consequences is acceptable.
+;;; 
+;;; 11. File is locked by calling user.  It looks unchanged, but is actually
+;;; changed.
+;;; 
+;;;    Potential cause: the file would have to be touched by a self-race
+;;; during window Q.
+;;; 
+;;;    The revert will succeed, removing whatever changes came with
+;;; the touch.  It is theoretically possible that work could be lost.
+;;; 
+;;; 12. File looks like it's locked by the calling user and unchanged, but
+;;; it's actually locked by someone else.
+;;; 
+;;;    Potential cause: a steal-lock in window V.
+;;; 
+;;;    RCS: co error: revision <rev> locked by <user>; use co -r or rcs -u
+;;;    SCCS: fails with error un2
+;;; 
+;;;    We can pass these errors up to the user.
+;;; 
+;;; Apparent state D ---
+;;;
+;;; 13. File looks like it's locked by the calling user and changed, but it's
+;;; actually unregistered.
+;;; 
+;;;    Potential cause: master file got nuked during window P.
+;;; 
+;;;    RCS: Checks in the user's version as an initial delta.
+;;;    SCCS: will fail with error ut4.
+;;;
+;;;    This case is kind of nasty.  It means VC may fail to detect the
+;;; loss of previous version information.
+;;; 
+;;; 14. File looks like it's locked by the calling user and changed, but it's
+;;; actually unlocked.
+;;; 
+;;;    Potential cause: self-race in window V, or the checkin happening
+;;; during the window X of someone else's steal-lock or window S of
+;;; someone else's revert.
+;;; 
+;;;    RCS: ci will fail with "no lock set by <user>".
+;;;    SCCS: delta will fail with error ut4.
+;;; 
+;;; 15. File looks like it's locked by the calling user and changed, but it's
+;;; actually locked by the calling user and unchanged.
+;;; 
+;;;    Potential cause: another self-race --- a whole checkin/checkout
+;;; sequence by the calling user would have to land in window R.
+;;; 
+;;;    SCCS: checks in a redundant delta and leaves the file unlocked as usual.
+;;;    RCS: reverts to the file state as of the second user's checkin, leaving
+;;; the file unlocked.
+;;;
+;;;    It is theoretically possible that work could be lost under RCS.
+;;; 
+;;; 16. File looks like it's locked by the calling user and changed, but it's
+;;; actually locked by a different user.
+;;; 
+;;;    RCS: ci error: no lock set by <user>
+;;;    SCCS: unget will fail with error un2
+;;; 
+;;;    We can pass these errors up to the user.
+;;; 
+;;; Apparent state E ---
+;;;
+;;; 17. File looks like it's locked by some other user, but it's actually
+;;; unregistered.
+;;; 
+;;;    As case 13.
+;;; 
+;;; 18. File looks like it's locked by some other user, but it's actually
+;;; unlocked.
+;;; 
+;;;    Potential cause: someone released a lock during window W.
+;;; 
+;;;    RCS: The calling user will get the lock on the file.
+;;;    SCCS: unget -n will fail with cm4.
+;;; 
+;;;    Either of these consequences will be OK.
+;;; 
+;;; 19. File looks like it's locked by some other user, but it's actually
+;;; locked by the calling user and unchanged.
+;;; 
+;;;    Potential cause: the other user relinquishing a lock followed by
+;;; a self-race, both in window W.
+;;; 
+;;;     Under both RCS and SCCS, both unlock and lock will succeed, making
+;;; the sequence a no-op.
+;;; 
+;;; 20. File looks like it's locked by some other user, but it's actually
+;;; locked by the calling user and changed.
+;;; 
+;;;     As case 19.
+;;; 
+;;; PROBLEM CASES:
+;;; 
+;;;    In order of decreasing severity:
+;;; 
+;;;    Cases 11 and 15 under RCS are the only one that potentially lose work.
+;;; They would require a self-race for this to happen.
+;;; 
+;;;    Case 13 in RCS loses information about previous deltas, retaining
+;;; only the information in the current workfile.  This can only happen
+;;; if the master file gets nuked in window P.
+;;; 
+;;;    Case 3 in RCS and case 15 under SCCS insert a redundant delta with
+;;; no change comment in the master.  This would require a self-race in
+;;; window P or R respectively.
+;;; 
+;;;    Cases 2, 10, 19 and 20 do extra work, but make no changes.
+;;; 
+;;;    Unfortunately, it appears to me that no recovery is possible in these
+;;; cases.  They don't yield error messages, so there's no way to tell that
+;;; a race condition has occurred.
+;;; 
+;;;    All other cases don't change either the workfile or the master, and
+;;; trigger command errors which the user will see.
+;;; 
+;;;    Thus, there is no explicit recovery code.
+
+;;; vc.el ends here