[patch] Question on resolving links?

[Rasmus <rasmus@gmx.us>]

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Hi,

I would like to use #+INCLUDE keywords for inputting headlines from
other files.  Line-numbers are too volatile and I'm not willing to
split up my file.

The attached patch does not, but I am not very happy about the
elegance of the implementation and it relies on a mix of org.el
functions and ox functions.  Basically, the patch tries to interpret
keywords like this:

#+INCLUDE: "~/file.org::*foo"

Is there not a function to interpret a link-string, say
"~/file.org::*foo", particularly with ox?  The closes thing I found
was `org-element-parse-secondary-string` on [[~/file.org::*foo]] which
gives me the correct element.
Normally, `org-export-resolve-fuzzy-link' should then help me out, but
in `org-export-expand-include-keyword' I don't have info!  Also,
`org-link-search' didn't seem to work across files.

Am I missing something obvious or is there a function I can study to
better understand how to resolve links?

Thanks,
Rasmus

-- 
In theory, practice and theory are the same. In practice they are not

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From f8dadcc363e4ad3fc102d1cbf200b6ff8344184d Mon Sep 17 00:00:00 2001
From: Rasmus <rasmus@gmx.us>
Date: Sat, 20 Sep 2014 22:22:15 +0200
Subject: [PATCH 2/2] ox: Allow headline links with #+INCLUDE

* ox.el (org-export-expand-include-keyword): Resolve headline
	links.

Accept keywords like "#+INCLUDE: file1.org::head1".  head1 must be a
CUSTOM_ID or resolvable by `org-link-search'.
---
 lisp/ox.el | 55 +++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 41 insertions(+), 14 deletions(-)

diff --git a/lisp/ox.el b/lisp/ox.el
index 55c02eb..bdcdc71 100644
--- a/lisp/ox.el
+++ b/lisp/ox.el
@@ -3322,19 +3322,46 @@ paths."
 	  ;; Extract arguments from keyword's value.
 	  (let* ((value (org-element-property :value element))
 		 (ind (org-get-indentation))
+		 headline-id
 		 (file (and (string-match
 			     "^\\(\".+?\"\\|\\S-+\\)\\(?:\\s-+\\|$\\)" value)
-			    (prog1 (expand-file-name
-				    (org-remove-double-quotes
-				     (match-string 1 value))
-				    dir)
-			      (setq value (replace-match "" nil nil value)))))
+			    (let ((matched (save-match-data
+					     (org-split-string (match-string 1 value) "::"))))
+			      (setq headline-id (car-safe (cdr-safe matched)))
+			      (prog1 (expand-file-name
+				      (org-remove-double-quotes
+				       (car matched))
+				      dir)
+				(setq value (replace-match "" nil nil value))))))
 		 (lines
-		  (and (string-match
-			":lines +\"\\(\\(?:[0-9]+\\)?-\\(?:[0-9]+\\)?\\)\""
-			value)
-		       (prog1 (match-string 1 value)
-			 (setq value (replace-match "" nil nil value)))))
+		  ;; (or
+		  ;; (and (string-match ":headline" value)
+		  ;; 	(error "#+INCLUDE can only have :lines /or/ :headline"))
+		  (prog1
+		      (if (string-match
+			   ":lines +\"\\(\\(?:[0-9]+\\)?-\\(?:[0-9]+\\)?\\)\""
+			   value)
+			(if headline-id
+			    (error "You have specified a headline and :lines in #+INCLUDE.")
+			  (match-string 1 value)
+			  (setq value (replace-match "" nil nil value)))
+			(save-window-excursion
+			  (find-file file)
+			  (let* ((data (org-element-parse-buffer))
+				 (headline
+				  (or ;; FIXME: there *must* be a better way to do this
+				   (org-element-map data 'headline
+				     (lambda (head) (when (equal headline-id
+							    (org-element-property :CUSTOM_ID head))
+						 head))
+				     nil 'first-match)
+				   (and (org-link-search headline-id) (org-element-at-point)))))
+			    (when (equal 'headline (org-element-type  headline))
+			      (mapconcat 'number-to-string
+					 (list
+					  (line-number-at-pos (org-element-property :begin headline))
+					  (line-number-at-pos (org-element-property :end headline)))
+					 "-")))))))
 		 (env (cond ((string-match "\\<example\\>" value)
 			     'literal)
 			    ((string-match "\\<src\\(?: +\\(.*\\)\\)?" value)
@@ -3371,8 +3398,8 @@ paths."
 		(insert
 		 (let ((ind-str (make-string ind ? ))
 		       (arg-str (if (stringp src-args)
-				  (format " %s" src-args)
-				""))
+				    (format " %s" src-args)
+				  ""))
 		       (contents
 			(org-escape-code-in-string
 			 (org-export--prepare-file-contents file lines))))
@@ -3382,7 +3409,7 @@ paths."
 		(insert
 		 (let ((ind-str (make-string ind ? ))
 		       (contents
-			 (org-export--prepare-file-contents file lines)))
+			(org-export--prepare-file-contents file lines)))
 		   (format "%s#+BEGIN_%s\n%s%s#+END_%s\n"
 			   ind-str block contents ind-str block))))
 	       (t
@@ -3853,7 +3880,7 @@ INFO is a plist used as a communication channel."
   (unless (org-export-get-node-property :UNNUMBERED headline t)
       (let ((sec-num (plist-get info :section-numbers))
 		 (level (org-export-get-relative-level headline info)))
-	     (if (wholenump sec-num) (<= level sec-num) sec-num)))))
+	     (if (wholenump sec-num) (<= level sec-num) sec-num))))
 
 (defun org-export-number-to-roman (n)
   "Convert integer N into a roman numeral."
-- 
2.1.0