> In practice only a subset of these grafts are applied because, for
> instance, Fish doesn’t depend (directly or indirectly) on Ghostscript at
> run time whereas it does depend on Perl:
> 
> --8<---------------cut here---------------start------------->8---
> $ guix gc -R $(guix build fish) | grep -E '(perl|ghostscript)'
> /gnu/store/7ifc22sh86zblnzamqimgmv06idyx69v-perl-5.26.1
> --8<---------------cut here---------------end--------------->8---

Thanks for pointing out this nuance, I wasn't aware of it.

But I still wonder: why is fish first built to
vgrav12zra9zky21ahm4x1qg8g4v58fj... and then immediately grafted to
avk637800w1n7z1z0hnzx80r0fpd6729... Why not building directly to
avk637800w1n7z1z0hnzx80r0fpd6729...?

I might be misunderstanding the basics of grafting :p

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