unexpected reproducibility of reproducible blog post?

[Leo Prikler <leo.prikler@student.tugraz.at>]

Hi simon,

I've executed your commands, et voilà
yours: /gnu/store/klisfr3a4wxb9dc5sgibb45kky72kg65-docker-pack.tar
mine:  /gnu/store/klisfr3a4wxb9dc5sgibb45kky72kg65-docker-pack.tar
Unsurprisingly, this did not change when adding channels -- though, if
you were to add your personal channel with some override for gcc-
toolchain, things might be different.

I don't know, what configuration exactly went into the blog post, but I
assume, it is not the same as for the time-machine experiments before. 
Since the prefix `guix time-machine --channels=guix-version-for-
reproduction.txt --` appears to be missing from the command, that hash
is therefore probably not indicative of anything.

I think the larger problem here is that, while Guix itself is
reproducible, Guix + org-mode (specifically the latter) is not. 
Particularly, looking at the source[1,2], it appears as if all code
blocks were evaluated once, but evaluating them again in a new
environment would bring different results.  In other words, you'd have
to use `guix time-machine` inside `guix time-machine` to get a truly
reproducibly org-mode file, or else come up with a smart way of
dynamically updating the hash in the source blocks themselves.

All the best,
Leo

[1] https://lists.gnu.org/archive/html/guix-devel/2020-01/msg00106.html
[2] 
https://github.com/khinsen/reproducibility-with-guix/blob/master/reproducibility-with-guix.org