Update installation command for Determinate Nix

[grahamc]

Removed the '--prefer-upstream-nix' option from the installation command.

Description

Checklist

• Formatted with cargo fmt
• Built with nix build
• Ran flake checks with nix flake check
• Added or updated relevant tests (leave unchecked if not applicable)
• Added or updated relevant documentation (leave unchecked if not applicable)
• Linked to related issues (leave unchecked if not applicable)

Validating with install.determinate.systems

If a maintainer has added the upload to s3 label to this PR, it will become available for installation via install.determinate.systems:

curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix/pr/$PR_NUMBER | sh -s -- install

Summary by CodeRabbit

• Documentation
  • Updated installation command in README for a simplified setup process.

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

[coderabbitai]

Walkthrough

The README.md installation command is updated by removing the --prefer-upstream-nix flag from the one-liner installer. This change causes the default behavior to switch from preferring upstream Nix to using Determinate Nix as the standard installation option.

Changes

Cohort / File(s)	Change Summary
README Update README.md	Removed --prefer-upstream-nix flag from the one-liner installer command, changing the default installation to use Determinate Nix instead of upstream Nix

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Possibly related PRs

• Default to Determinate Nix #1692 — Defaults prefer_upstream to false and switches installer defaults to Determinate Nix, aligning with this README change
• Add an option to prefer upstream Nix, implementing ItS#3 part one #1664 — Introduces the prefer_upstream/--prefer-upstream-nix option and associated logic that this README change references
• docs: Passing --prefer-upstream-nix to install for upstream Nix #1715 — Modifies the same README installer command around the --prefer-upstream-nix flag usage

Poem

🐰 A flag hops away with a bound,
The nix installs smoothly, profound,
Determinate leads the way,
No upstream delay,
Simpler defaults all around! 🎯

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title directly and clearly summarizes the main change: updating the installation command for Determinate Nix by removing the --prefer-upstream-nix flag.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch grahamc-patch-2

---

📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 3e92fe5 and 50ae07b.

📒 Files selected for processing (1)

• README.md (1 hunks)

🧰 Additional context used

🧠 Learnings (2)

📓 Common learnings

Learnt from: grahamc
Repo: DeterminateSystems/nix-installer PR: 1664
File: src/settings.rs:56-67
Timestamp: 2025-09-10T15:49:03.281Z
Learning: In the nix-installer codebase, the prefer_upstream CLI flag is intentionally designed as a presence-only flag. Users wanting Determinate Nix should use --determinate instead of --prefer-upstream=false, as this was a deliberate UX design choice to keep the interface simpler.

📚 Learning: 2025-09-10T15:49:03.281Z

Learnt from: grahamc
Repo: DeterminateSystems/nix-installer PR: 1664
File: src/settings.rs:56-67
Timestamp: 2025-09-10T15:49:03.281Z
Learning: In the nix-installer codebase, the prefer_upstream CLI flag is intentionally designed as a presence-only flag. Users wanting Determinate Nix should use --determinate instead of --prefer-upstream=false, as this was a deliberate UX design choice to keep the interface simpler.

Applied to files:

• README.md

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (4)

• GitHub Check: build-aarch64-darwin / Build aarch64 Darwin (static)
• GitHub Check: build-aarch64-linux / Build aarch64 Linux (static)
• GitHub Check: build-x86_64-linux / Build x86_64 Linux (static)
• GitHub Check: Lints

🔇 Additional comments (1)

README.md (1)

23-23: Aligns with PR objective and maintains documentation consistency.

The removal of --prefer-upstream-nix from the default quick-start command makes Determinate Nix the default installation option, which aligns with the PR objective. The supporting documentation for upstream Nix installation (lines 438–442) and the flag definition in the settings table (line 390) remain intact, preserving the ability for users to opt into upstream Nix until January 1, 2026.

Please confirm that:

1. The --prefer-upstream-nix flag still exists in the CLI code and behaves as documented
2. The installation works as expected without the flag (installs Determinate Nix by default)

You can verify this by checking if the flag is still defined in the settings or argument parser code.

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}