Add completion for 'doas' to pcomplete

* lisp/pcmpl-unix.el (pcomplete/doas): New function.
* etc/NEWS: Announce.  (Bug#66551)
Co-authored-by: Visuwesh <visuweshm@gmail.com>

etc/NEWS

@@ -491,6 +491,10 @@ When this option is non-nil, remote file names are not completed by
 Pcomplete.  Packages, like 'shell-mode', could set this in order to
 suppress remote file name completion at all.
 
+---
+*** Completion for the 'doas' command has been added.
+Command completion for 'doas' in Eshell and Shell mode will now work.
+
 ** Shell Mode
 
 +++

lisp/pcmpl-unix.el

@@ -685,6 +685,14 @@ Includes files as well as host names followed by a colon."
   (funcall (or (pcomplete-find-completion-function (pcomplete-arg 1))
 	       pcomplete-default-completion-function)))
 
+;;;###autoload
+(defun pcomplete/doas ()
+  "Completion for the `doas' command."
+  (pcomplete-opt "C(pcomplete-entries)Lnsu(pcmpl-unix-user-names)")
+  (funcall pcomplete-command-completion-function)
+  (funcall (or (pcomplete-find-completion-function (pcomplete-arg 1))
+               pcomplete-default-completion-function)))
+
 (provide 'pcmpl-unix)
 
 ;;; pcmpl-unix.el ends here