(vc-buffer-sync): Signal error if user says no.

1 files changed, 35 insertions, 8 deletions

diff --git a/lisp/vc.el b/lisp/vc.el
index e9501a8bd0b..7b688ea8694 100644
--- a/lisp/vc.el
+++ b/lisp/vc.el
@@ -118,6 +118,12 @@ 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.")
 
+;; Default is to be extra careful for super-user.
+(defvar vc-checkout-carefully (= (user-uid) 0)
+  "*Non-nil means be extra-careful in checkout.
+Verify that the file really is not locked
+and that its contents match what the master file says.")
+
 ;; Variables the user doesn't need to know about.
 (defvar vc-log-entry-mode nil)
 (defvar vc-log-operation nil)
@@ -327,12 +333,12 @@ the master name of FILE; this is appended to an optional list of FLAGS."
 
 (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)))
+  (if (buffer-modified-p)
+      (progn
+        (or vc-suppress-confirm
+            (y-or-n-p (format "Buffer %s modified; save it? " (buffer-name)))
+            (error "Aborted"))
+        (save-buffer))))
 
 (defun vc-workfile-unchanged-p (file)
   ;; Has the given workfile changed since last checkout?
@@ -365,7 +371,26 @@ the master name of FILE; this is appended to an optional list of FLAGS."
 
      ;; if there is no lock on the file, assert one and get it
      ((not (setq owner (vc-locking-user file)))
-      (vc-checkout-writable-buffer file))
+      (if (and vc-checkout-carefully
+               (not (vc-workfile-unchanged-p file))
+               (not (zerop (vc-backend-diff file nil))))
+          (if (save-window-excursion
+                (pop-to-buffer "*vc*")
+                (goto-char (point-min))
+                (insert-string (format "Changes to %s since last lock:\n\n"
+                                       file))
+                (not (beep))
+                (yes-or-no-p
+                      (concat "File has unlocked changes, "
+                       "claim lock retaining changes? ")))
+              (progn (vc-backend-steal file)
+                     (vc-mode-line file))
+            (if (not (yes-or-no-p "Revert to checked-in version, instead? "))
+                (error "Checkout aborted.")
+              (vc-revert-buffer1 t t)
+              (vc-checkout-writable-buffer file))
+            )
+        (vc-checkout-writable-buffer file)))
 
      ;; a checked-out version exists, but the user may not own the lock
      ((not (string-equal owner (user-login-name)))
@@ -441,7 +466,9 @@ it will operate on the file in the current line.
 files are marked, it will accept a log message and then operate on
 each one.  The log message will be used as a comment for any register
 or checkin operations, but ignored when doing checkouts.  Attempted
-lock steals will raise an error."
+lock steals will raise an error.
+
+   For checkin, a prefix argument lets you specify the version number to use."
   (interactive "P")
   (catch 'nogo
     (if vc-dired-mode