Fix Nix version parsing for prereleases that omit the patch component

[mikeland73]

Summary

Fixes #2766.

Modern Nix prerelease versions report a version string that omits the patch component, e.g. nix (Nix) 2.33pre20251107_479b6b73 (2.33 rather than 2.33.0). Devbox's versionRegexp required a MAJOR.MINOR.PATCH core, so these versions failed to parse. As a result Info.Version came back empty and EnsureNixInstalled aborted with:

Error: Devbox requires nix of version >= 2.12.0. Your version is . Please upgrade nix and try again.

even though the installed Nix was perfectly recent enough.

Changes

• versionRegexp: make the patch component optional so 2.33pre20251107_479b6b73 parses and Info.Version is populated correctly.
• Info.AtLeast: when coercing a patch-less Nix prerelease to a valid semver for comparison, inject a .0 patch (2.33-pre.20251107+479b6b73 → 2.33.0-pre.20251107+479b6b73), since golang.org/x/mod/semver requires a patch component when a prerelease is present. A new missingPatchRegexp handles this.
• Added test coverage in nix/nix_test.go for both parsing and AtLeast comparisons of the patch-less prerelease format.

Testing

go test ./nix/
go vet ./nix/

Both pass.

cc @Electrenator (issue reporter)

---

Generated by Claude Code

[Copilot]

Pull request overview

This PR fixes Devbox’s Nix version detection for prerelease version strings that omit the patch component (e.g. 2.33pre20251107_479b6b73), ensuring Info.Version is populated and EnsureNixInstalled no longer fails version checks incorrectly.

Changes:

• Updated versionRegexp to allow parsing MAJOR.MINOR prerelease forms (optional patch component).
• Updated Info.AtLeast to coerce patch-less versions into valid semver by inserting a .0 patch before comparing.
• Added tests covering parsing and comparisons for the patch-less prerelease format.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
nix/nix.go	Expands Nix version parsing and semver comparison to handle prereleases missing the patch component.
nix/nix_test.go	Adds regression tests for parsing and AtLeast comparisons for patch-less prerelease versions.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[mikeland73]

Heads-up on CI: the only failing check (test … project-tests-only) fails solely on the Elixir example (development_elixir_elixir_hello_run_test), and the failure is unrelated to this change:

** (Mix) httpc request failed with: {:failed_connect, [{:to_address, {~c"builds.hex.pm", 443}}, ...
   {:tls_alert, {:unsupported_certificate, ... key_usage_mismatch ...}}]}
Could not install Hex because Mix could not download metadata at https://builds.hex.pm/installs/hex-1.x.csv

Mix/Erlang is rejecting builds.hex.pm's TLS certificate (server-auth vs keyCertSign/cRLSign key-usage mismatch). All other example tests and the unit tests pass, and this reproduced identically across two runs — so it's an external infra issue affecting main and every PR equally, not something in this diff. This PR only touches nix/nix.go version parsing (covered by the passing go test ./nix/).

---

Generated by Claude Code