walking up the filetree (in a Guix related package)

[ng0 <contact.ng0@cryptolab.net>]

Hi,

in https://github.com/neomutt/neomutt/pull/527 I'm trying to add a file
to neomutt which can be used to build the current checkout with Guix,
skipping the hash check.

This is very similar to what I use in the gnURL release procedure,
but it has one defect: It requires that the file is located in the
top sourcedirectory / root directory of the source.

I'm trying to change this:

(define %source-dir (dirname (current-filename)))

so that it interacts with the (source (local-file))
of the package and allows the package to sit in contrib/guix-neomutt.scm,
but I'm not sure how this can be achieved. All ways I've tried failed
so far. What part of the Guile documentation could help?

For the Guix list and cross subscribed people: did we introduce something
in Guix recently which maybe makes this way of defining the source obsolete?

Thanks!
-- 
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