Valodim: interestingly this does not work. 

```
$ cat ~/.nix-profile/etc/profile.d/hm-session-vars.sh 
# Only source this once.
if [ -n "$__HM_SESS_VARS_SOURCED" ]; then return; fi
export __HM_SESS_VARS_SOURCED=1

export EDITOR="vim"
export FOO="bar"
export SSH_AUTH_SOCK="$(/nix/store/rvv06zyqi2sqf7bp32byr3q415vg574b-gnupg-2.2.17/bin/gpgconf --list-dirs agent-ssh-socket)"
```

in this file you see that it sets a `...SOURCED=1` var to avoid setting these values again. interestingly, i have no FOO available in my gnome shell, but the SOURCED=1 value is set, so sourcing that file again has no effect...