How to specify several lines via extra-conf in /etc/nix/nix.conf ?

[teto]

maybe a duplicate of #425 but how to add several lines to nix.conf ?

I would like a better example in README/builtin help: I tried
sh ./nix-rust-installer.sh install --extra-conf "experimental-features = nix-command flakes" --extra-conf "extra-substituters = XXX"
but it fails.
I've tried sh ./nix-rust-installer.sh install --extra-conf 'experimental-features = nix-command flakes\nextra-substituters = XXX' but only 'experimental-features = nix-command flakes' got written to /etc/nix/nix.conf, the line after\n` got ignored.

Supporting several --extra-conf would be cleaner + be closer to nix --extra-XXX flags

[Hoverbear]

You may have found a bug!

You should be able to set --extra-conf multiple times:

nix-installer/src/settings.rs

Lines 184 to 185 in 4cc8326

	#[cfg_attr(feature = "cli", clap(long, action = ArgAction::Set, num_args = 0.., value_delimiter = ',', env = "NIX_INSTALLER_EXTRA_CONF", global = true))]
	pub extra_conf: Vec<String>,

And we should join those together:

nix-installer/src/action/common/place_nix_configuration.rs

Lines 28 to 31 in 4cc8326

	let extra_conf = extra_conf.join("\n");
	let mut nix_config = nix_config_parser::NixConfig::parse_string(extra_conf, None)
	.map_err(CreateOrMergeNixConfigError::ParseNixConfig)
	.map_err(Self::error)?;

My suspicion is that this is a bug in the nix-config-parser we've been developing. We already set --extra-conf "experimental-features = nix-command flakes" so it's possible the parser is somehow dropping part of the input in it's deduplication process. Could you try not passing that and just passing the extra-substitutors one?

@cole-h maybe this is something you'd be interested in looking at?