greedy substitution in org-open-file

[Maxim Nikulin]

Looking into the code related to 'pty problem with 
start-process-shell-command, I have realized that the following case is 
not handled correctly:

#+begin_src elisp
  (setq org-file-apps '(("\\.pdf::\\([0-9]+\\)\\'" . "xpdf %s %1")))
#+end_src

I hope, I adapted an example from [[help:org-file-apps]] correctly. When 
I try to open the following link using C-c C-o

[[file:test-%1f.pdf::42]]

I get

Running xpdf /home/ubuntu/examples/org/test-\42f.pdf 42...done

I believe, it should be

Running xpdf /home/ubuntu/examples/org/test-%1f.pdf 42...done

Or

Running xpdf /home/ubuntu/examples/org/test-\%1f.pdf 42...done

Org mode version 9.4.4 (release_9.4.4-164-g7a9a8a

The source of the problem is that %s substitution is expanded at first 
and regexp groups are replaced later. Ideally, it should be performed in 
a single pass. I have found format-spec function but I am unsure 
concerning it, maybe it is avoided intentionally.