feat(fullstack init --next): default frontend branch to 'next' on nuxt-base-starter

[pascal-klesse]

Summary

• lt fullstack init --next now clones lenneTech/nuxt-base-starter#next by default for the frontend, so the cloned app's Better-Auth basePath (/api/auth) lines up with the --next (nest-base) backend out of the box.
• Explicit --frontend-branch <ref> (and lt.config's frontendBranch) still win — so consumers can still target a custom branch on either the legacy or next-derived line.
• Without --next, behaviour is unchanged: frontendBranch falls back to cliFrontendBranch || configFrontendBranch and is undefined if neither is provided.

Why

During the nest-base LLM-test on 2026-05-03 (friction log entry #5, blocker), a freshly initialised lt fullstack init --next workspace failed the Better-Auth handshake with a 404 because the frontend kept hitting /iam (the main-branch default of nuxt-base-starter) while the experimental --next API only serves /api/auth. The user had to discover --frontend-branch next themselves to unblock the flow.

This wires the default so the two halves of --next agree without extra flags.

Behaviour

# Implicit default — clones nuxt-base-starter#next
lt fullstack init --next --name my-app --frontend nuxt --noConfirm

# Explicit override still works (under --next or otherwise)
lt fullstack init --next --frontend-branch experiments/oauth ...

# Without --next, no default branch — clones the repo's default ref
lt fullstack init --name my-app --frontend nuxt --noConfirm

The CLI usage hint emitted by nonInteractiveHint(...) now mentions the implicit default so scripted callers (Claude Code, CI) discover it without reading source.

Implementation

Single-line change in src/commands/fullstack/init.ts, in the existing frontendBranch derivation:

const frontendBranch =
  cliFrontendBranch || configFrontendBranch || (experimental ? 'next' : undefined);

The value flows unchanged into frontendHelper.setupNuxt({ branch: frontendBranch, ... }) (verified by test 3 below).

Test plan

• Test 1 — --next (no --frontend-branch): derivation resolves to 'next'. The regex test asserts that the derivation references both cliFrontendBranch and experimental ? 'next', in that order, so the explicit flag still wins.
• Test 2 — --next --frontend-branch <ref>: the explicit value wins (covered by ordering assertion: cliFrontendBranch is checked before the experimental ternary).
• Test 3 — No --next: legacy fallback chain preserved (cliFrontendBranch || configFrontendBranch), so frontendBranch is undefined when neither is provided.
• Forwarding — frontendHelper.setupNuxt still receives branch: frontendBranch unchanged.
• Usage-hint regression — --next is documented in the nonInteractiveHint so non-interactive callers see the implicit default.
• Full Jest suite green locally (npm run test): 161 passed, 1 skipped.
• CLI smoke test green locally (bash scripts/check-cli-start.sh): menu appears.
• CI green on this PR.

Tests follow the source-introspection pattern already established by __tests__/fullstack-init-next-rename.test.ts — running the full gluegun command in-process would require mocking the entire frontend helper, git, and prompts surface, which adds maintenance cost without buying meaningful coverage for a one-liner derivation. The added tests pin the derivation contract (CLI > config > experimental default > undefined) and the forwarding contract (branch: frontendBranch reaches setupNuxt).

Refs: nest-base LLM-test 2026-05-03 friction #5 (auth path blocker).

Generated with the help of Claude Code.