Hi,
Darlan Cavalcante Moreira <darcamo@gmail.com> writes:

> I have this
>   #+LINK: attach elisp:(org-open-file (org-attach-expand "%s"))
> in all of my org-mode files. In fact, I have this line, among others, in
> an org-mode setup file which is included in all of my org-mode files
> using "#+SETUPFILE:"
>
> Then I can create a link to an attachment with
> [[attach:filename_without_any_path.extension][description]]
>
> Also, just after attaching a new file org will automatically store the
> link so that you can use "C-c C-l" to include the link.
I like your solution, but I was quite frustrated by the lack of
completion against the attached files,

Here, I propose a solution using `org-add-link-type' and adding
"attach:" kind of links.

I actually propose to patch org mode to add this feature. I realized
that the part about finding the attached file was already implemented
into `org-attach-open', so I first extracted the functionality into a
separated function, then I made use of it to implement the new "attach:"
link and the associated completion.

For that reason, I split the work into two commits that you'll find
attached to this mail.