BEFORE `guix pill`:
$ guix --version
guix (GNU Guix) 1.0.1
Copyright (C) 2019 the Guix authors
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ guix describe
guix describe: error: failed to determine origin
hint: Perhaps this `guix' command was not obtained with `guix pull'? Its version
string is 1.0.1.
$ which guix
/usr/local/bin/guix
$ readlink -f `which guix`
/gnu/store/ncknl03pkmamrxg7q9nxi1rn1qhvwbi9-guix-1.0.1/bin/guix

AFTER `guix pull`:
$ guix --version
guix (GNU Guix) ecf3a3ac9b9ff7efa757b2f9b61edff58c3f60e5
Copyright (C) 2019 the Guix authors
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ guix describe
Generation 1    Oct 11 2019 09:18:11    (current)
  guix ecf3a3a
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: ecf3a3ac9b9ff7efa757b2f9b61edff58c3f60e5
$ which guix
/root/.config/guix/current/bin/guix
$ readlink -f `which guix`
/gnu/store/gz2kxgkxdn4iyjbifgi6ca6byl81agwq-guix-command