doc: Update the template fetch snippet

[foo-dogsquared]

It creates an UndefinedVar error for me. Tested on Nix v2.3.10 and unstable version of Nix just to be sure.

[nrdxp]

Thanks for the report. Are your refering to:

nix-shell https://github.com/divnix/devos/archive/core.tar.gz -A shell \
  --run "flk get core"

?

If so, I cannot reproduce this error, even after a fresh garbage collection. What's your OS and Arch.

[codygman]

I think @foo-dogsquared means the one without quotes before the change:

 nix-shell -p cachix --run cachix use nrdxp 

This one gives the error:

devos  cody 「↪ 𝚫 ⟫8 」  ⎔ on  (us-east-1) 
✖1 ❯  nix-shell -p cachix --run cachix use nrdxp 
error: --- UndefinedVarError ------------------------------------------------------------------- nix-shell
at: (1:103) from string

     1| with import <nixpkgs> { }; (pkgs.runCommandCC or pkgs.runCommand) "shell" { buildInputs = [ (cachix) (use) (nrdxp) ]; } ""
      |                                                                                                       ^

undefined variable 'use'
(use '--show-trace' to show detailed location information)

[nrdxp]

Just needed some quotes.