ob-screen: Accept :screenrc header argument

* lisp/ob-screen.el (org-babel-default-header-args:screen): Add
default header argument `:screenrc' and value "/dev/null".
(org-babel-prep-session:screen): Use header argument in variable
`screenrc' and not hard-coded value.

etc/ORG-NEWS

@@ -229,6 +229,12 @@ directory configured for ClojureScript will /not/ work.
 Babel Java blocks recognize header argument =:cmdargs= and pass its
 value in call to =java=.
 
+*** =ob-screen.el=: Screen now accepts =:screenrc= header argument
+
+Screen blocks now recognize the =:screenrc= header argument and pass
+its value to the screen command via the "-c" option. The default
+remains =/dev/null= (i.e. a clean screen session)
+
 *** =RET= and =C-j= now obey ~electric-indent-mode~
 
 Since Emacs 24.4, ~electric-indent-mode~ is enabled by default.  In

lisp/ob-screen.el

@@ -40,7 +40,8 @@
 In case you want to use a different screen than one selected by your $PATH")
 
 (defvar org-babel-default-header-args:screen
-  '((:results . "silent") (:session . "default") (:cmd . "sh") (:terminal . "xterm"))
+  '((:results . "silent") (:session . "default") (:cmd . "sh")
+    (:terminal . "xterm") (:screenrc . "/dev/null"))
   "Default arguments to use when running screen source blocks.")
 
 (defun org-babel-execute:screen (body params)
@@ -59,10 +60,11 @@ In case you want to use a different screen than one selected by your $PATH")
   (let* ((session (cdr (assq :session params)))
          (cmd (cdr (assq :cmd params)))
          (terminal (cdr (assq :terminal params)))
+         (screenrc (cdr (assq :screenrc params)))
          (process-name (concat "org-babel: terminal (" session ")")))
     (apply 'start-process process-name "*Messages*"
            terminal `("-T" ,(concat "org-babel: " session) "-e" ,org-babel-screen-location
-		      "-c" "/dev/null" "-mS" ,session ,cmd))
+		      "-c" ,screenrc "-mS" ,session ,cmd))
     ;; XXX: Is there a better way than the following?
     (while (not (org-babel-screen-session-socketname session))
       ;; wait until screen session is available before returning