ol-man.el: Enable completion

* lisp/ol-man.el (org-man-complete): New function implementing
completion for man pages using `Man-completion-table'.  Set this
function as the `:complete' property of "man" links.

Ihor Radchenko. Re: Completion of links to man pages.
Sat, 09 Dec 2023 11:32:39 +0000.
<https://list.orgmode.org/877clnsjag.fsf@localhost>

etc/ORG-NEWS

@@ -729,6 +729,12 @@ respected.
 Images dropped also respect the value of ~org-yank-image-save-method~
 when ~org-yank-dnd-method~ is =attach=.
 
+*** Add completion for links to man pages
+
+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.
+
 ** New functions and changes in function arguments
 *** ~org-fold-hide-drawer-all~ is now interactive
 

lisp/ol-man.el

@@ -34,6 +34,7 @@
 (require 'ol)
 
 (org-link-set-parameters "man"
+                         :complete #'org-man-complete
 			 :follow #'org-man-open
 			 :export #'org-man-export
 			 :store #'org-man-store-link)
@@ -99,6 +100,17 @@ BACKEND is the current export backend."
      ((eq backend 'md) (format "[%s](%s)" desc path))
      (t path))))
 
+(defun org-man-complete (&optional _arg)
+  "Complete man pages for `org-insert-link'."
+  (require 'man)
+  (concat
+   "man:"
+   (let ((completion-ignore-case t) ; See `man' comments.
+         (Man-completion-cache)) ; See `man' implementation.
+     (completing-read
+      "Manual entry: "
+      'Man-completion-table))))
+
 (provide 'ol-man)
 
 ;;; ol-man.el ends here