Pure repl can't load locked flake

[roberth]

Describe the bug

Pure repl can't load locked flake.

Steps To Reproduce

Steps to reproduce:

1. Lock a local flake.
2. Load it into a pure repl

$ nix repl --option pure-eval true --pure-eval
Welcome to Nix 2.18.1. Type :? for help.

nix-repl> :lf .
error: cannot use ':load-flake' on locked flake reference '.' (use --impure to override)

nix-repl> :please?

Expected behavior

Pure repl can load a locked flake from a relative path

Pure repl can not load an unlocked flake from anywhere. This part already works. (It doesn't seem to be an errant boolean negation)

nix-env --version output

Additional context

Priorities

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[thufschmitt]

Discussed during the Nix maintenance team meeting on 2024-01-12. Approved and open for contributions

- @thufschmitt: The issue seems to be that the url itself is impure - Would still make sense to allow at toplevel - Idea approved

[nixos-discourse]

This issue has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/2021-01-11-nix-team-meeting-minutes-115/38277/1