(vc-version-other-window): New function.

(vc-backend-checkout): Add optional arg workfile, which specifies where
to put the working file.

diff --git a/lisp/vc.el b/lisp/vc.el
index d0f7d77..0a15abf 100644 (file)
--- a/lisp/vc.el
+++ b/lisp/vc.el
@@ -806,6 +806,26 @@ files in or below it."
        (message "No changes to %s between %s and %s." file rel1 rel2)
       (pop-to-buffer "*vc*"))))
 
+;;;###autoload
+(defun vc-version-other-window (rev)
+  "Visit version REV of the current buffer in another window.
+If the current buffer is named `F', the version is named `F.~REV~'.
+If `F.~REV~' already exists, it is used instead of being re-created."
+  (interactive "sVersion to visit (default is latest version): ")
+  (if vc-dired-mode
+      (set-buffer (find-file-noselect (dired-get-filename))))
+  (while vc-parent-buffer
+      (pop-to-buffer vc-parent-buffer))
+  (if (and buffer-file-name (vc-name buffer-file-name))
+      (let* ((version (if (string-equal rev "")
+                         (vc-latest-version buffer-file-name)
+                       rev))
+            (filename (concat buffer-file-name ".~" version "~")))
+        (or (file-exists-p filename)
+            (vc-backend-checkout buffer-file-name nil version filename))
+        (find-file-other-window filename))
+    (vc-registration-error buffer-file-name)))
+
 ;; Header-insertion code
 
 ;;;###autoload
@@ -1423,21 +1443,42 @@ Return nil if there is no such person."
   (message "Registering %s...done" file)
   )
 
-(defun vc-backend-checkout (file &optional writable rev)
+(defun vc-backend-checkout (file &optional writable rev workfile)
   ;; Retrieve a copy of a saved version into a workfile
-  (message "Checking out %s..." file)
-  (vc-backend-dispatch file
-   (progn
+  (let ((filename (or workfile file)))
+    (message "Checking out %s..." filename)
+    (vc-backend-dispatch file
      (vc-do-command 0 "get" file       ;; SCCS
                    (if writable "-e")
+                   (if workfile  (concat "-G" workfile))
                    (and rev (concat "-r" (vc-lookup-triple file rev))))
+     (if workfile ;; RCS
+        ;; RCS doesn't let us check out into arbitrary file names directly.
+        ;; Use `co -p' and make stdout point to the correct file.
+        (let ((default-modes (default-file-modes))
+              (vc-modes (logior (file-modes (vc-name file))
+                                (if writable 128 0)))
+              (failed t))
+          (unwind-protect
+              (progn
+                  (set-default-file-modes vc-modes)
+                  (vc-do-command
+                     0 "/bin/sh" file "-c"
+                     "filename=$1; shift; exec co \"$@\" >$filename"
+                     "" ; dummy argument for shell's $0
+                     filename
+                     (if writable "-l")
+                     (concat "-p" rev))
+                  (setq failed nil))
+            (set-default-file-modes default-modes)
+            (and failed (file-exists-p filename) (delete-file filename))))
+       (vc-do-command 0 "co" file
+                     (if writable "-l")
+                     (and rev (concat "-r" rev))))
      )
-   (vc-do-command 0 "co" file  ;; RCS
-                 (if writable "-l")
-                 (and rev (concat "-r" rev)))
-   )
-  (vc-file-setprop file 'vc-checkout-time (nth 5 (file-attributes file)))
-  (message "Checking out %s...done" file)
+    (or workfile
+       (vc-file-setprop file 'vc-checkout-time (nth 5 (file-attributes file))))
+    (message "Checking out %s...done" filename))
   )
 
 (defun vc-backend-logentry-check (file)
@@ -1572,6 +1613,7 @@ These bindings are added to the global keymap when you enter this mode:
 \\[vc-revert-buffer]           revert buffer to latest version
 \\[vc-cancel-version]          undo latest checkin
 \\[vc-diff]            show diffs between file versions
+\\[vc-version-other-window]            visit old version in another window
 \\[vc-directory]               show all files locked by any user in or below .
 \\[vc-update-change-log]               add change log entry from recent checkins