diff -u /home/oub/emacs/site-lisp/versch/add-ons/vc-rcs.el /home/oub/emacs/site-lisp/versch/add-ons/vc-rcs-new.el
--- /home/oub/emacs/site-lisp/versch/add-ons/vc-rcs.el	2015-09-06 16:19:54.780811291 +0200
+++ /home/oub/emacs/site-lisp/versch/add-ons/vc-rcs-new.el	2015-09-06 16:27:04.662942964 +0200
@@ -106,6 +106,58 @@
   :group 'vc-rcs)
 
 
+
+;; new variable for changing the login user
+
+
+(defvar vc-rcs-ask-for-login nil
+  "*Variable which allows to change the login Id by a y-or-n question.")
+
+(defvar vc-rcs-login-user nil 
+  "*Variable which saves the value of the rcs user who checks in.")
+
+
+;; since changing the (login) user is not a frequent thing to do, the following functions
+;; toggle this behaviour on an off
+
+;; the following function was written by Adrian Kubala
+;; <adrian@sixfingeredman.net>
+
+(defun make-repeat-command (symbol command-list)
+  "Command changes with each repetition.
+SYMBOL is a symbol unique to this command."
+  (if (eq last-command symbol)
+      (set symbol (+ (eval symbol) 1))
+    (set symbol 0))
+  (if (>= (eval symbol) (length command-list))
+      (set symbol 0))
+  (call-interactively (nth (eval symbol) command-list))
+  (setq this-command symbol))
+
+
+(defun vc-rcs-set-for-login ()
+  (interactive)
+  (load-file "~/emacs/site-lisp/versch/vc-change-login.elc")
+  (setq vc-rcs-ask-for-login t)
+  (message "Now login will be changed when vc-rcs-checkin is called."))
+
+(defun vc-rcs-remove-for-login () 
+  (interactive)
+  (setq vc-rcs-ask-for-login nil)
+  (message "Now login will  *NOT* be changed when vc-rcs-checkin is called."))
+
+
+(defun vc-ask-login-or-not ()
+  (interactive)
+  (make-repeat-command 'vc-ask-login-or-not
+		       '(vc-rcs-set-for-login
+                         vc-rcs-remove-for-login)))
+
+
+;; end of toggling functions
+
+
+
 ;;; Properties of the backend
 
 (defun vc-rcs-revision-granularity () 'file)
@@ -309,9 +361,11 @@
 ;; It used to be possible to pass in a value for the variable rev, but
 ;; nothing in the rest of VC used this capability.  Removing it makes the
 ;; backend interface simpler for all modes.
-;;
+;; modified 
 (defun vc-rcs-checkin (files comment)
-  "RCS-specific version of `vc-backend-checkin'."
+  "RCS-specific version of `vc-backend-checkin'. If the variable
+vc-rcs-ask-for-login is set to t, function asks for user login.
+Useful for collaboration to distinguish different checkins."
   (let (rev (switches (vc-switches 'RCS 'checkin)))
     ;; Now operate on the files
     (dolist (file (vc-expand-dirs files 'RCS))
@@ -331,6 +385,12 @@
 	       ;; if available, use the secure check-in option
 	       (and (vc-rcs-release-p "5.6.4") "-j")
 	       (concat "-u" rev)
+	       (if vc-rcs-ask-for-login 
+		   (if (y-or-n-p (format "Do you want to change the login  "))
+		       (progn
+			 (setq vc-rcs-login-user (read-string "Enter New login: ")) 
+			 (concat "-w" vc-rcs-login-user))
+		     (concat "-m" comment)))
 	       (concat "-m" comment)
 	       switches)
 	(vc-file-setprop file 'vc-working-revision nil)

Diff finished.  Sun Sep  6 16:27:33 2015