org-footnote-new: Add an option to create new anonymous labels

* lisp/org-footnote.el (org-footnote-new, org-footnote-auto-label):
Add symbol `anonymous' to `org-footnote-auto-label'.  With this,
anonymous footnotes will be created.  This is sometimes useful in long
texts.  Mimics \footnote{} in LaTeX.  Modify `org-footnote-new' to
generate anonymous footnotes directly.

* lisp/org.el (org-startup-options): Add `fnanon' to startup options.

* testing/lisp/test-org-footnote.el (test-org-footnote/new-anon): Add
a test for creation of anonymous footnotes.

* etc/ORG-NEWS:
(~org-footnote-new~ can be configured to create anonymous footnotes):
Announce new anonymous footnote support.

* doc/org-manual.org (Summary of In-Buffer Settings): Document
"fnanon" startup option.

doc/org-manual.org

@@ -20381,6 +20381,7 @@ changes.
   | =fnconfirm=  | Offer automatic label for editing or confirmation.     |
   | =fnadjust=   | Automatically renumber and sort footnotes.             |
   | =nofnadjust= | Do not renumber and sort automatically.                |
+  | =fnanon=     | Create anonymous footnotes with ~org-footnote-new~.    |
 
   #+vindex: org-hide-block-startup
   #+vindex: org-hide-drawer-startup

etc/ORG-NEWS

@@ -917,6 +917,14 @@ Completion is enabled for links to man pages added using ~org-insert-link~:
 =C-c C-l man RET emacscl TAB= to get =emacsclient=.  Of course, the ~ol-man~
 library should be loaded first.
 
+*** ~org-footnote-new~ can be configured to create anonymous footnotes
+
+When ~org-footnote-auto-label~ is set to ~'anonymous~, create
+anonymous footnotes automatically with ~org-footnote-new~.
+
+The same can be done via startup options:
+: #+STARTUP: fnanon
+
 ** New functions and changes in function arguments
 *** New API functions to store data within ~org-element-cache~
 

lisp/org-footnote.el

@@ -137,6 +137,7 @@ Possible values are:
 
 nil        Prompt the user for each label.
 t          Create unique labels of the form [fn:1], [fn:2], etc.
+anonymous  Create anonymous footnotes
 confirm    Like t, but let the user edit the created value.
            The label can be removed from the minibuffer to create
            an anonymous footnote.
@@ -146,6 +147,7 @@ random	   Automatically generate a unique, random label."
 	  (const :tag "Prompt for label" nil)
 	  (const :tag "Create automatic [fn:N]" t)
 	  (const :tag "Offer automatic [fn:N] for editing" confirm)
+	  (const :tag "Create anoymous [fn::]" anonymous)
 	  (const :tag "Create a random label" random))
   :safe #'symbolp)
 
@@ -666,15 +668,16 @@ or new, let the user edit the definition of the footnote."
     (user-error "Cannot insert a footnote here"))
   (let* ((all (org-footnote-all-labels))
 	 (label
-	  (if (eq org-footnote-auto-label 'random)
+          (unless (eq org-footnote-auto-label 'anonymous)
-	      (format "%x" (abs (random)))
+	    (if (eq org-footnote-auto-label 'random)
-	    (org-footnote-normalize-label
+	        (format "%x" (abs (random)))
-	     (let ((propose (org-footnote-unique-label all)))
+	      (org-footnote-normalize-label
-	       (if (eq org-footnote-auto-label t) propose
+	       (let ((propose (org-footnote-unique-label all)))
-		 (completing-read
+	         (if (eq org-footnote-auto-label t) propose
-		  "Label (leave empty for anonymous): "
+		   (completing-read
-		  (mapcar #'list all) nil nil
+		    "Label (leave empty for anonymous): "
-		  (and (eq org-footnote-auto-label 'confirm) propose))))))))
+		    (mapcar #'list all) nil nil
+		    (and (eq org-footnote-auto-label 'confirm) propose)))))))))
     (cond ((not label)
 	   (insert "[fn::]")
 	   (backward-char 1))

lisp/org.el

@@ -4125,6 +4125,7 @@ After a match, the following groups carry important information:
     ("fnplain" org-footnote-auto-label plain)
     ("fnadjust" org-footnote-auto-adjust t)
     ("nofnadjust" org-footnote-auto-adjust nil)
+    ("fnanon" org-footnote-auto-label anonymous)
     ("constcgs" constants-unit-system cgs)
     ("constSI" constants-unit-system SI)
     ("noptag" org-tag-persistent-alist nil)

testing/lisp/test-org-footnote.el

@@ -21,6 +21,18 @@
 
 (require 'org-footnote)
 
+(ert-deftest test-org-footnote/new-anon ()
+  "Test `org-footnote-new' specifications."
+  ;; `org-footnote-auto-label' is `anonymous'.
+  (should
+   (string-match-p
+    "Test\\[fn::\\]"
+    (org-test-with-temp-text "Test<point>"
+      (let ((org-footnote-auto-label 'anonymous)
+	    (org-footnote-section nil))
+	(org-footnote-new))
+      (buffer-string)))))
+
 (ert-deftest test-org-footnote/new ()
   "Test `org-footnote-new' specifications."
   ;; `org-footnote-auto-label' is t.