nix daemon vs nix-daemon

[bryanhonof]

Problem

I can't see if there's a difference between the nix-daemon and nix daemon command.
The current documentation of both looks quite similar, but it doesn't seem both accept the same flags.
E.g. I can pass --stdio to nix-daemon, but not to nix daemon.

$ # Just waits for connections, or user interrupt
$ nix-daemon --stdin

$ nix daemon --stdio
error: unrecognised flag '--stdio'
Try 'nix --help' for more information.

Proposal

Clarify which flags both command accept, and what their intended use-cases are.

Checklist

• checked latest Nix manual (source)
• checked open documentation issues and pull requests for possible duplicates

Priorities

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Ref #7128

[bryanhonof]

The relevant code is located here, at least, I believe so.

nix/src/nix/daemon.cc

Lines 471 to 490 in 635df5e

	parseCmdLine(argc, argv, [&](Strings::iterator & arg, const Strings::iterator & end) {
	if (*arg == "--daemon")
	; // ignored for backwards compatibility
	else if (*arg == "--help")
	showManPage("nix-daemon");
	else if (*arg == "--version")
	printVersion("nix-daemon");
	else if (*arg == "--stdio")
	stdio = true;
	else if (*arg == "--force-trusted") {
	experimentalFeatureSettings.require(Xp::DaemonTrustOverride);
	isTrustedOpt = Trusted;
	} else if (*arg == "--force-untrusted") {
	experimentalFeatureSettings.require(Xp::DaemonTrustOverride);
	isTrustedOpt = NotTrusted;
	} else if (*arg == "--default-trust") {
	experimentalFeatureSettings.require(Xp::DaemonTrustOverride);
	isTrustedOpt = std::nullopt;
	} else return false;
	return true;