docs: Passing --prefer-upstream-nix to install for upstream Nix

[sestrella]

The command example in the README file to install upstream Nix is not up to date, because the default distribution when --prefer-upstream-nix is not passed to install is Distribution::DeterminateNix.

nix-installer/src/settings.rs

Lines 324 to 334 in 91e0774

	pub fn distribution(&self) -> Distribution {
	if self.determinate_nix {
	Distribution::DeterminateNix
	} else if self.prefer_upstream {
	// If the user passed --prefer-upstream (or it defaults to true), default back to Nix
	Distribution::Nix
	} else {
	Distribution::DeterminateNix
	}
	}
	}

Future Changes?

Given that Distribution::DeterminateNix is the default distribution and the installer only supports two distributions for the time being, the logic to determine which distribution to install could be simplified a bit by removing the --determinate flag.

if self.prefer_upstream {
  Distribution::Nix
} else {
  Distribution::DeterminateNix
}

Additionally, a more general flag like --distribution <determinate|upstream> could be used instead of --determinate and --prefer-upstream-nix to allow for greater flexibility in the future. This could be addressed in a separate PR if the proposed changes make sense, as the primary goal of this one was to update the documentation.

Summary by CodeRabbit

• Documentation
  • Updated example command in README with the --prefer-upstream-nix flag option.

_{✏️ Tip: You can customize this high-level summary in your review settings.}

[coderabbitai]

Walkthrough

The README.md documentation is updated to include the --prefer-upstream-nix flag in an example curl command for upstream Nix installations. This reflects an available CLI option in the documentation without any code or behavioral changes.

Changes

Cohort / File(s)	Summary
Documentation README.md	Added --prefer-upstream-nix flag to example curl command

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Possibly related PRs

• Add an option to prefer upstream Nix, implementing ItS#3 part one #1664: Implements the prefer_upstream CLI option that is now documented in the README example
• Default to Determinate Nix #1692: Modifies the behavior and defaults of the prefer_upstream CLI option reflected in this documentation update

Suggested reviewers

• cole-h
• colemickens

Poem

🐰 A flag appears in docs so bright,
--prefer-upstream-nix takes flight!
Examples updated, crystal clear,
Users now know options here. 📖✨

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The title accurately describes the main documentation change: adding --prefer-upstream-nix flag to the install example in README.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[grahamc]

Thank you for the fix!