Refactor Org Mode link finder function

The main entry point is now `db/org-find-links-to-current-item', which decides
how to obtain the ID and CUSTOM_ID of the item to look for.  The main work is
done by `db/org-find-items-linking-to-id', which does some checks, build the
query, and then calls `org-search-view' (which, indeed, does the actual work).
Users should call `db/org-find-links-to-current-item' only.

init.el

@@ -716,7 +716,7 @@
              db/org-mark-current-default-task
              db/export-diary
              db/org-copy-template-for-periodic-task
-             db/org-find-items-linking-to-id))
+             db/org-find-links-to-current-item))
 
 (use-package org
   :pin "gnu"

site-lisp/db-org.el

@@ -595,22 +595,13 @@ This is done only if the value of this variable is not null."
 
 ;;; Find items by link to current headline
 
-(defun db/org-find-items-linking-by-id (&optional id custom-id)
+(defun db/org-find-items-linking-by-id (id custom-id)
   "List all Org Mode items that link to ID.
 Uses `org-search-view' to conduct the actual search.  ID must be
 a UUID as generated by, e.g., `org-id-get-create', and CUSTOM-ID
-must consist of ASCII letters, numbers, and hyphens only.  When
-called interactively in Org Mode, use the values ID and CUSTOM_ID
-of the current item.  When called interactively outside of Org
-Mode, prompt the user for the user for a headline."
-  (interactive (if (derived-mode-p 'org-mode)
-                   (list (org-id-get) (org-entry-get nil "CUSTOM_ID"))
-                 (let ((pom (nth 3 (org-refile-get-location))))
-                   (if (not pom)
-                       (user-error "Invalid location")
-                     (org-with-point-at pom
-                       (list (org-id-get) (org-entry-get nil "CUSTOM_ID")))))))
-
+must consist of ASCII letters, numbers, and hyphens only.  Each
+of ID and CUSTOM-ID may be nil, but at least one of them must be
+not."
   (unless (or (not id)
               (and (stringp id)
                    (string-match-p  "^[a-f0-9]\\{8\\}-[a-f0-9]\\{4\\}-[a-f0-9]\\{4\\}-[a-f0-9]\\{4\\}-[a-f0-9]\\{12\\}$" id)))
@@ -628,6 +619,22 @@ Mode, prompt the user for the user for a headline."
                 (t (user-error "No ID given and not in Org Mode.")))))
     (org-search-view nil query)))
 
+(defun db/org-find-links-to-current-item (arg)
+  "Find links to current item.
+Only links using the ID or CUSTOM_ID property are considered.
+
+If ARG is given, or if not in an Org Mode buffer, interactively
+prompt for an item."
+  (interactive "P")
+  (apply #'db/org-find-items-linking-by-id
+         (if (and (derived-mode-p 'org-mode) (not arg))
+             (list (org-id-get) (org-entry-get nil "CUSTOM_ID"))
+           (let ((pom (nth 3 (org-refile-get-location))))
+             (if (not pom)
+                 (user-error "Invalid location")
+               (org-with-point-at pom
+                 (list (org-id-get) (org-entry-get nil "CUSTOM_ID"))))))))
+
 
 ;;; End