[bug#45018] [PATCH 2/6] daemon: Use 'Agent' to spawn 'guix substitute --query'.

[Mathieu Othacehe]

Hey,

> +         (("--substitute" store-path destination)
> +          ;; Download STORE-PATH and add store it as a Nar in file 
> DESTINATION.

add it to store?

> +     const Strings args = { "substitute", "--query" };
> +     const std::map<string, string> env = { { "_NIX_OPTIONS", 
> settings.pack() } };
> +     std::unique_ptr<Agent>fresh(new Agent(settings.guixProgram, args, env));

You should prefer make_unique to "new" calls.

> -     std::unique_ptr<RunningSubstituter>fresh(new RunningSubstituter);
> +     const Strings args = { "substitute", "--query" };
> +     const std::map<string, string> env = { { "_NIX_OPTIONS", 
> settings.pack() } };
> +     std::unique_ptr<Agent>fresh(new Agent(settings.guixProgram, args, env));

Ditto.

Thanks,

Mathieu