guix describe -p and Guix commit?

[zimoun <zimon.toutoune@gmail.com>]

Dear,

How to track from which channel and commit the packages in a profile come from?

For example, today (time T) I run:
  guix package -i emacs guile -p my-env
And I forgot to store the result of "guix describe".

Months later, and after several "guix pull" and not changing the
profile "my-env", I would like to reproduce this exact profile on
another machine.

It is easy to extract the version of Emacs and Guile:
  guix describe -p my-env

So I can dig in the git history to find the commit introducing the
specific version of Emacs and Guile. Well it is not convenient. :-)
but doable. Then, I run:
  guix pull --commit=<hash>
  guix package -i emacs guile -p my-new-env

It is also possible to extract the hashes in the store, reading the
file my-env/manifest and my-new-env/manifest.
And they are not the same. The Guix version that I just pulled should
be anterior to the one at time T. Because maybe something in the
dependencies of Emacs or Guile has changed.

Well, I can list all the pulls with "guix pull" and then guess some
commit. But it is not convenient, neither.

What I would expect is:
 guix describe -p my-env
Generation 5   Sep 20 2019 17:21:30
emacs 26.2 asdf12
guile 2.2.4 z56qwe

(for example, I updated only Emacs once, 3 times Guile)


What do you think?
Do it make sense?


All the best,
simon


All the best,
simon