ox-latex: New function to generate header

* ox-latex.el (org-latex--make-header): New function.
  (org-latex-template): Use new function.
* ox-koma-letter.el (org-koma-letter-template): Use new function.

contrib/lisp/ox-koma-letter.el

@@ -592,27 +592,7 @@ holding export options."
    (and (plist-get info :time-stamp-file)
         (format-time-string "%% Created %Y-%m-%d %a %H:%M\n"))
    ;; Document class and packages.
-   (let* ((class (plist-get info :latex-class))
-	  (class-options (plist-get info :latex-class-options))
-	  (header (nth 1 (assoc class org-latex-classes)))
-	  (document-class-string
-	   (and (stringp header)
-		(if (not class-options) header
-		  (replace-regexp-in-string
-		   "^[ \t]*\\\\documentclass\\(\\(\\[[^]]*\\]\\)?\\)"
-		   class-options header t nil 1)))))
-     (if (not document-class-string)
-	 (user-error "Unknown LaTeX class `%s'" class)
-       (org-latex-guess-babel-language
-	(org-latex-guess-inputenc
-	 (org-element-normalize-string
-	  (org-splice-latex-header
-	   document-class-string
-	   org-latex-default-packages-alist ; Defined in org.el.
-	   org-latex-packages-alist nil     ; Defined in org.el.
-	   (concat (org-element-normalize-string (plist-get info :latex-header))
-		   (plist-get info :latex-header-extra)))))
-	info)))
+   (org-latex--make-header info)
    ;; Settings.  They can come from three locations, in increasing
    ;; order of precedence: global variables, LCO files and in-buffer
    ;; settings.  Thus, we first insert settings coming from global

lisp/ox-latex.el

@@ -1467,21 +1467,10 @@ INFO is a plist used as a communication channel."
       (?L . ,(capitalize language))
       (?D . ,(org-export-get-date info)))))
 
-
-;;; Template
-
-(defun org-latex-template (contents info)
-  "Return complete document string after LaTeX conversion.
-CONTENTS is the transcoded contents string.  INFO is a plist
-holding export options."
-  (let ((title (org-export-data (plist-get info :title) info))
-	(spec (org-latex--format-spec info)))
-    (concat
-     ;; Time-stamp.
-     (and (plist-get info :time-stamp-file)
-	  (format-time-string "%% Created %Y-%m-%d %a %H:%M\n"))
-     ;; Document class and packages.
-     (let* ((class (plist-get info :latex-class))
+(defun org-latex--make-header (info)
+  "Return a formatted LaTeX header.
+INFO is a plist used as a communication channel."
+  (let* ((class (plist-get info :latex-class))
 	    (class-options (plist-get info :latex-class-options))
 	    (header (nth 1 (assoc class (plist-get info :latex-classes))))
 	    (document-class-string
@@ -1504,7 +1493,23 @@ holding export options."
 		       (plist-get info :latex-header))
 		      (plist-get info :latex-header-extra)))))
 	   info)
-	  info)))
+	  info))))
+
+
+;;; Template
+
+(defun org-latex-template (contents info)
+  "Return complete document string after LaTeX conversion.
+CONTENTS is the transcoded contents string.  INFO is a plist
+holding export options."
+  (let ((title (org-export-data (plist-get info :title) info))
+	(spec (org-latex--format-spec info)))
+    (concat
+     ;; Time-stamp.
+     (and (plist-get info :time-stamp-file)
+	  (format-time-string "%% Created %Y-%m-%d %a %H:%M\n"))
+     ;; Document class and packages.
+     (org-latex--make-header info)
      ;; Possibly limit depth for headline numbering.
      (let ((sec-num (plist-get info :section-numbers)))
        (when (integerp sec-num)