(tags-loop-revert-buffers): Value `ask' means to query the user interactively.

(next-file): Implement it.

diff --git a/lisp/progmodes/etags.el b/lisp/progmodes/etags.el
index 32aecdd8295bebac92f31ffafc916e135870f95d..d69d1de6cdce7e411fcf838c68cf8fe09aebc86c 100644 (file)
--- a/lisp/progmodes/etags.el
+++ b/lisp/progmodes/etags.el
@@ -1629,12 +1629,14 @@ where they were found."
       (and (search-forward "\177" (save-excursion (end-of-line) (point)) t)
           (re-search-backward re bol t)))))
 \f
-(defcustom tags-loop-revert-buffers nil
-  "*Non-nil means tags-scanning loops should offer to reread changed files.
-These loops normally read each file into Emacs, but when a file
-is already visited, they use the existing buffer.
-When this flag is non-nil, they offer to revert the existing buffer
-in the case where the file has changed since you visited it."
+(defcustom tags-loop-revert-buffers 'ask
+  "Whether the tags-scanning loop should reread changed files.
+This loop normally reads each file into Emacs, but when a file is
+already visited, it uses the existing buffer.
+If this variable is nil, the loop uses the existing buffer even
+if the file has changed since you visited it.
+If the value is `ask', the loop offers to revert the buffer.
+Any other non-nil value means to revert the buffer automatically."
   :type 'boolean
   :group 'etags)
 
@@ -1696,6 +1698,14 @@ if the file was newly read in, the value is the filename."
     ;; if the files have changed on disk.
     (and buffer tags-loop-revert-buffers
         (not (verify-visited-file-modtime buffer))
+        (or (not (eq tags-loop-revert-buffers 'ask))
+            noninteractive
+            (y-or-n-p
+             (format
+              (if (buffer-modified-p buffer)
+                  "File %s changed on disk.  Discard your edits? "
+                "File %s changed on disk.  Reread from disk? ")
+              next)))
         (with-current-buffer buffer
           (revert-buffer t)))
     (if (not (and new novisit))