Find the last revision attached.  I've taken all comments into
consideration and I'm quite happy with the result.

I've found a much better advanced example: libgit2.
The only thing is... it does not pass the tests.

In guix, libgit2 uses an archive upstream.  I've changed the package to
check out the git repository.  Only then the test fail:

--8<---------------cut here---------------start------------->8---
starting phase `check'
Loaded 341 suites: 
Started

apply::fromdiff...................
apply::fromfile..........................................
attr::file....
attr::flags...
attr::ignoreF

  1) Failure:
attr::ignore::honor_temporary_rules [/tmp/guix-build-my-libgit2-0.26.6-1.e98d0a3.drv-0/my-libgit2-0.26.6-1.e98d0a3-checkout/tests/clar_libgit2.c:47]
  Expression is not true: (fd = p_open(path, flags, mode)) >= 0
--8<---------------cut here---------------end--------------->8---

Any clue?
I'll keep investigating tomorrow.  Once this is fixed, it should be
ready for publication.

-- 
Pierre Neidhardt
https://ambrevar.xyz/