Find rcs2log in the source-directory when running uninstalled

This is preparation for getting rid of lib-src's "stamp-*" files.

* lisp/vc/vc-rcs.el (vc-rcs-rcs2log-program): New.
(vc-rcs-update-changelog): Use it.

2 files changed, 22 insertions, 4 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 59039e19ab2..211ea180ec4 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,8 @@
 2012-06-06  Glenn Morris  <rgm@gnu.org>
 
+        * vc/vc-rcs.el (vc-rcs-rcs2log-program): New.
+        (vc-rcs-update-changelog): Use it.
+
         * emacs-lisp/authors.el (authors-fixed-entries): Remove vcdiff
 
         * vc/vc-sccs.el (vc-sccs-write-revision): New function.
diff --git a/lisp/vc/vc-rcs.el b/lisp/vc/vc-rcs.el
index 7e10372f362..104e6fd59e3 100644
--- a/lisp/vc/vc-rcs.el
+++ b/lisp/vc/vc-rcs.el
@@ -1,6 +1,6 @@
 ;;; vc-rcs.el --- support for RCS version-control
 
-;; Copyright (C) 1992-2012  Free Software Foundation, Inc.
+;; Copyright (C) 1992-2012 Free Software Foundation, Inc.
 
 ;; Author:     FSF (see vc.el for full credits)
 ;; Maintainer: Andre Spiegel <spiegel@gnu.org>
@@ -868,6 +868,23 @@ and CVS."
           (minor-num (string-to-number (vc-rcs-minor-part rev))))
       (concat branch "." (number-to-string (1+ minor-num))))))
 
+;; Note that most GNU/Linux distributions seem to supply rcs2log in a
+;; standard bin directory.  Eg both Red Hat and Debian include it in
+;; their cvs packages.  It's not obvious why Emacs still needs to
+;; provide it as well...
+(defvar vc-rcs-rcs2log-program
+  (let (exe)
+    (cond ((file-executable-p
+            (setq exe (expand-file-name "rcs2log" exec-directory)))
+           exe)
+          ;; In the unlikely event that someone is running an
+          ;; uninstalled Emacs and wants to do something RCS-related.
+          ((file-executable-p
+            (setq exe (expand-file-name "lib-src/rcs2log" source-directory)))
+           exe)
+          (t "rcs2log")))
+  "Path to the `rcs2log' program (normally in `exec-directory').")
+
 (defun vc-rcs-update-changelog (files)
   "Default implementation of update-changelog.
 Uses `rcs2log' which only works for RCS and CVS."
@@ -898,9 +915,7 @@ Uses `rcs2log' which only works for RCS and CVS."
              (unwind-protect
                  (progn
                    (setq default-directory odefault)
-                   (if (eq 0 (apply 'call-process
-                                    (expand-file-name "rcs2log"
-                                                      exec-directory)
+                   (if (eq 0 (apply 'call-process vc-rcs-rcs2log-program
                                     nil (list t tempfile) nil
                                     "-c" changelog
                                     "-u" (concat login-name