org.el: Use nil as the default value for `org-link-to-org-use-id'

* org.el (org-link-to-org-use-id): Move to org-id.el.

* org-id.el (org-id-link-to-org-use-id): Rename from
`org-link-to-org-use-id'.  Use `nil' as the default value.
(org-link-to-org-use-id): Alias and define as obsolete.

`org-link-to-org-use-id' was previously defined in org.el but only
active when org-id.el was loaded.  This is wrong.  It now belongs
to org-id.el.

Also, as some libraries require org-id.el on the fly, a non-nil
default value for `org-link-to-org-use-id' had the side-effect of
changing the behavior of `org-store-link' behind the user's back.
Which is wrong too.  The new default value is `nil' so that, even
when a library requires org-id.el without the user noticing it,
the behavior of `org-store-link' will not change.

Users who want to keep the previous behavior can set the variable
to 'create-if-interactive-and-no-custom-id

INCOMPATIBLE

lisp/org-id.el

@@ -83,6 +83,46 @@
   :tag "Org ID"
   :group 'org)
 
+(define-obsolete-variable-alias
+  'org-link-to-org-use-id 'org-id-link-to-org-use-id "24.3")
+(defcustom org-id-link-to-org-use-id nil
+  "Non-nil means storing a link to an Org file will use entry IDs.
+
+The variable can have the following values:
+
+t     Create an ID if needed to make a link to the current entry.
+
+create-if-interactive
+      If `org-store-link' is called directly (interactively, as a user
+      command), do create an ID to support the link.  But when doing the
+      job for capture, only use the ID if it already exists.  The
+      purpose of this setting is to avoid proliferation of unwanted
+      IDs, just because you happen to be in an Org file when you
+      call `org-capture' that automatically and preemptively creates a
+      link.  If you do want to get an ID link in a capture template to
+      an entry not having an ID, create it first by explicitly creating
+      a link to it, using `C-c C-l' first.
+
+create-if-interactive-and-no-custom-id
+      Like create-if-interactive, but do not create an ID if there is
+      a CUSTOM_ID property defined in the entry.  This is the default.
+
+use-existing
+      Use existing ID, do not create one.
+
+nil   Never use an ID to make a link, instead link using a text search for
+      the headline text."
+  :group 'org-link-store
+  :group 'org-id
+  :type '(choice
+	  (const :tag "Create ID to make link" t)
+	  (const :tag "Create if storing link interactively"
+		 create-if-interactive)
+	  (const :tag "Create if storing link interactively and no CUSTOM_ID is present"
+		 create-if-interactive-and-no-custom-id)
+	  (const :tag "Only use existing" use-existing)
+	  (const :tag "Do not use ID to create link" nil)))
+
 (defcustom org-id-uuid-program "uuidgen"
   "The uuidgen program."
   :group 'org-id

lisp/org.el

@@ -1447,46 +1447,6 @@ It should match if the message is from the user him/herself."
   :group 'org-link-store
   :type 'regexp)
 
-(defcustom org-link-to-org-use-id 'create-if-interactive-and-no-custom-id
-  "Non-nil means storing a link to an Org file will use entry IDs.
-
-Note that before this variable is even considered, org-id must be loaded,
-so please customize `org-modules' and turn it on.
-
-The variable can have the following values:
-
-t     Create an ID if needed to make a link to the current entry.
-
-create-if-interactive
-      If `org-store-link' is called directly (interactively, as a user
-      command), do create an ID to support the link.  But when doing the
-      job for capture, only use the ID if it already exists.  The
-      purpose of this setting is to avoid proliferation of unwanted
-      IDs, just because you happen to be in an Org file when you
-      call `org-capture' that automatically and preemptively creates a
-      link.  If you do want to get an ID link in a capture template to
-      an entry not having an ID, create it first by explicitly creating
-      a link to it, using `C-c C-l' first.
-
-create-if-interactive-and-no-custom-id
-      Like create-if-interactive, but do not create an ID if there is
-      a CUSTOM_ID property defined in the entry.  This is the default.
-
-use-existing
-      Use existing ID, do not create one.
-
-nil   Never use an ID to make a link, instead link using a text search for
-      the headline text."
-  :group 'org-link-store
-  :type '(choice
-	  (const :tag "Create ID to make link" t)
-	  (const :tag "Create if storing link interactively"
-		 create-if-interactive)
-	  (const :tag "Create if storing link interactively and no CUSTOM_ID is present"
-		 create-if-interactive-and-no-custom-id)
-	  (const :tag "Only use existing" use-existing)
-	  (const :tag "Do not use ID to create link" nil)))
-
 (defcustom org-context-in-file-links t
   "Non-nil means file links from `org-store-link' contain context.
 A search string will be added to the file name with :: as separator and
@@ -8890,7 +8850,8 @@ type.  For a simple example of an export function, see `org-bbdb.el'."
       (setcdr (assoc type org-link-protocols) (list follow export))
     (push (list type follow export) org-link-protocols)))
 
-(defvar org-agenda-buffer-name)
+(defvar org-agenda-buffer-name) ; Defined in org-agenda.el
+(defvar org-link-to-org-use-id) ; Defined in org-id.el
 
 ;;;###autoload
 (defun org-store-link (arg)