org-store-link: Don't roll C-u behavior into C-u C-u behavior

* lisp/org.el (org-store-link): When a double C-u prefix argument is
given, do not reverse the meaning of the org-context-in-file-links
option.
* testing/lisp/test-org.el (test-org/store-link): Add tests.

This allows the user to fall back to the core link storing functions
without also reversing their org-context-in-file-links preference,
because wanting to do the former does not mean a user also wants to do
the latter.

Reported-by: York Zhao <gtdplatform@gmail.com>
<https://lists.gnu.org/archive/html/emacs-orgmode/2017-05/msg00254.html>

lisp/org.el

@@ -9921,9 +9921,10 @@ and then used in capture templates."
 This link is added to `org-stored-links' and can later be inserted
 into an Org buffer with `org-insert-link' (`\\[org-insert-link]').
 
-For some link types, a `\\[universal-argument]' prefix ARG is interpreted.
-For links to Usenet articles, ARG negates `org-gnus-prefer-web-links'.
-For file links, ARG negates `org-context-in-file-links'.
+For some link types, a `\\[universal-argument]' prefix ARG is interpreted.  \
+A single
+`\\[universal-argument]' negates `org-context-in-file-links' for file links or
+`org-gnus-prefer-web-links' for links to Usenet articles.
 
 A `\\[universal-argument] \\[universal-argument]' prefix ARG forces \
 skipping storing functions that are not
@@ -10085,7 +10086,8 @@ active region."
 				(abbreviate-file-name
 				 (buffer-file-name (buffer-base-buffer)))))
 	   ;; Add a context search string
-	   (when (org-xor org-context-in-file-links arg)
+	   (when (org-xor org-context-in-file-links
+			  (equal arg '(4)))
 	     (let* ((element (org-element-at-point))
 		    (name (org-element-property :name element)))
 	       (setq txt (cond
@@ -10112,7 +10114,8 @@ active region."
 			     (abbreviate-file-name
 			      (buffer-file-name (buffer-base-buffer)))))
 	;; Add a context string.
-	(when (org-xor org-context-in-file-links arg)
+	(when (org-xor org-context-in-file-links
+		       (equal arg '(4)))
 	  (setq txt (if (org-region-active-p)
 			(buffer-substring (region-beginning) (region-end))
 		      (buffer-substring (point-at-bol) (point-at-eol))))

testing/lisp/test-org.el

@@ -2399,7 +2399,82 @@ http://article.gmane.org/gmane.emacs.orgmode/21459/"
      (org-test-with-temp-text-in-file "#+NAME: foo\nParagraph"
        (let ((file (buffer-file-name)))
 	 (equal (format "[[file:%s::foo][foo]]" file)
-		(org-store-link nil)))))))
+		(org-store-link nil))))))
+  ;; Store link to Org buffer, with context.
+  (should
+   (let ((org-stored-links nil)
+	 (org-id-link-to-org-use-id nil)
+	 (org-context-in-file-links t))
+     (org-test-with-temp-text-in-file "* h1"
+       (let ((file (buffer-file-name)))
+	 (equal (format "[[file:%s::*h1][h1]]" file)
+		(org-store-link nil))))))
+  ;; Store link to Org buffer, without context.
+  (should
+   (let ((org-stored-links nil)
+	 (org-id-link-to-org-use-id nil)
+	 (org-context-in-file-links nil))
+     (org-test-with-temp-text-in-file "* h1"
+       (let ((file (buffer-file-name)))
+	 (equal (format "[[file:%s][file:%s]]" file file)
+		(org-store-link nil))))))
+  ;; C-u prefix reverses `org-context-in-file-links' in Org buffer.
+  (should
+   (let ((org-stored-links nil)
+	 (org-id-link-to-org-use-id nil)
+	 (org-context-in-file-links nil))
+     (org-test-with-temp-text-in-file "* h1"
+       (let ((file (buffer-file-name)))
+	 (equal (format "[[file:%s::*h1][h1]]" file)
+		(org-store-link '(4)))))))
+  ;; A C-u C-u does *not* reverse `org-context-in-file-links' in Org
+  ;; buffer.
+  (should
+   (let ((org-stored-links nil)
+	 (org-id-link-to-org-use-id nil)
+	 (org-context-in-file-links nil))
+     (org-test-with-temp-text-in-file "* h1"
+       (let ((file (buffer-file-name)))
+	 (equal (format "[[file:%s][file:%s]]" file file)
+		(org-store-link '(16)))))))
+  ;; Store file link to non-Org buffer, with context.
+  (should
+   (let ((org-stored-links nil)
+	 (org-context-in-file-links t))
+     (org-test-with-temp-text-in-file "one\n<point>two"
+       (fundamental-mode)
+       (let ((file (buffer-file-name)))
+	 (equal (format "[[file:%s::one]]" file)
+		(org-store-link nil))))))
+  ;; Store file link to non-Org buffer, without context.
+  (should
+   (let ((org-stored-links nil)
+	 (org-context-in-file-links nil))
+     (org-test-with-temp-text-in-file "one\n<point>two"
+       (fundamental-mode)
+       (let ((file (buffer-file-name)))
+	 (equal (format "[[file:%s][file:%s]]" file file)
+	 	(org-store-link nil))))))
+  ;; C-u prefix reverses `org-context-in-file-links' in non-Org
+  ;; buffer.
+  (should
+   (let ((org-stored-links nil)
+	 (org-context-in-file-links nil))
+     (org-test-with-temp-text-in-file "one\n<point>two"
+       (fundamental-mode)
+       (let ((file (buffer-file-name)))
+	 (equal (format "[[file:%s::one]]" file)
+		(org-store-link '(4)))))))
+  ;; A C-u C-u does *not* reverse `org-context-in-file-links' in
+  ;; non-Org buffer.
+  (should
+   (let ((org-stored-links nil)
+	 (org-context-in-file-links nil))
+     (org-test-with-temp-text-in-file "one\n<point>two"
+       (fundamental-mode)
+       (let ((file (buffer-file-name)))
+	 (equal (format "[[file:%s][file:%s]]" file file)
+	 	(org-store-link '(16))))))))
 
 
 ;;; Node Properties