feat(core): broaden .understandignore starter for C#/Java/Go test patterns

[thejesh23]

Summary

• Detect C# project-suffix directories (Foo.Tests/, Foo.UnitTests/, Foo.IntegrationTests/) and PascalCase test dirs (Tests/, UnitTests/, IntegrationTests/) via case-insensitive match in generateStarterIgnoreFile.
• Restructure test-file suggestions into language groups (JS / TS, C# / .NET, Java / Kotlin, Go) with sub-headers.
• Extract skills/understand/generate-ignore.mjs so Phase 0.5 invokes @understand-anything/core instead of duplicating ~40 lines of generator logic in an inline node -e "…" block.

All suggestions remain commented-out — same opt-in model. No defaults change; no behaviour change for users with an existing .understandignore.

Motivation

.understandignore starter today only suggests JS/TS/Python-shaped patterns: lowercase exact-name dirs (tests, __tests__, fixtures) and dot-separated test file patterns (*.test.*, *.spec.*). For C# / Java / Go projects this misses common conventions:

Language	What was missed
C# / .NET	Tests/ (case-sensitive FS), Foo.Tests/, Foo.UnitTests/, *Tests.cs, *Test.cs, *.Tests.csproj
Java / Kotlin	src/test/, *Test.java, *IT.java, *Spec.kt
Go	*_test.go

Changes

packages/core/src/ignore-generator.ts

• Replaced hardcoded existsSync(join(root, dir)) probe with readdirSync(root, { withFileTypes: true }) + case-insensitive exact-name match + suffix-glob match.
• New EXACT_DIR_NAMES, SUFFIX_DIR_GLOBS, TEST_PATTERN_GROUPS constants.
• Emits directory matches using on-disk casing so users see Tests/ not tests/ when that's what they have.

packages/core/src/__tests__/ignore-generator.test.ts

• 14 new tests: PascalCase / C# project-suffix detection, language-grouped pattern emission, group ordering, all-commented invariant on empty dirs, suffix-glob rejects non-directory entries.
• All existing tests still pass; 753 tests total across the core package.

skills/understand/generate-ignore.mjs (new)

• Thin wrapper script invoked by SKILL.md Phase 0.5. Imports generateStarterIgnoreFile from @understand-anything/core via the same workspace-link → plugin-cache dist resolution pattern used by scan-project.mjs.
• Skips with a stderr notice if the target file already exists.

skills/understand/SKILL.md

• Phase 0.5 reduced from a 40-line inline node -e "…" block to one line: node <SKILL_DIR>/generate-ignore.mjs $PROJECT_ROOT. Single source of truth for ignore generation now lives in @understand-anything/core.

Out of scope (deliberate)

• bin/ in DEFAULT_IGNORE_PATTERNS — already flagged by @AsimRaza10 on How to make /understand run faster ? #76; leaving it for that thread.
• .gitignore runtime fallback for non-git projects — @AsimRaza10's PR.
• --exclude CLI flag — feat: add --exclude CLI flag to /understand for user-defined ignore p… #373.

Test plan

• pnpm --filter @understand-anything/core build — clean.
• pnpm --filter @understand-anything/core test — 753 tests pass (30 in ignore-generator.test.ts, including 14 new).
• pnpm lint — clean.
• Local smoke test: ran node skills/understand/generate-ignore.mjs /tmp/smoke against a directory with Tests/, MyApp.Tests/, UnitTests/, fixtures/ and a .gitignore. Output included # Tests/, # MyApp.Tests/, # UnitTests/, # fixtures/, .gitignore extraction, and language-grouped patterns in stable order — all commented out.
• Manual: end-to-end /understand run on a C# repo to confirm Phase 0.5 invokes the bundled script correctly.

Refs #76

🤖 Generated with Claude Code

[Lum1104]

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[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Use the resolved plugin root for copied skill installs

When the skill directory is copied to a runtime skills folder instead of symlinked under the plugin checkout, resolve(__dirname, '../..') points at that skills parent rather than the real plugin root. Phase 0 already supports those installs by resolving PLUGIN_ROOT from several locations, but this new Phase 0.5 helper ignores that value, so first-time runs with no .understandignore fail to resolve @understand-anything/core and then try a nonexistent packages/core/dist/index.js under the skills folder. Use the resolved plugin root or implement the same fallback search here before importing core.

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[thejesh23]

Good catch, addressed in 83d3fb6.

generate-ignore.mjs now prefers $PLUGIN_ROOT from the env (validated by checking for a package.json at that path) and falls back to the existing resolve(__dirname, '../..') heuristic. SKILL.md Phase 0.5 was updated to pass the env var:

PLUGIN_ROOT="$PLUGIN_ROOT" node <SKILL_DIR>/generate-ignore.mjs $PROJECT_ROOT

Smoke-tested both paths locally — the env-set path resolves through Phase 0's multi-candidate value; the fallback path matches prior behavior for standard installs. 753 tests still pass; lint clean.

Note: the same resolve(__dirname, '../..') pattern exists in scan-project.mjs, compute-batches.mjs, extract-import-map.mjs, extract-structure.mjs, and build-fingerprints.mjs. They share the same latent issue but kept out of this PR's scope — happy to file a follow-up to harden them uniformly if the maintainers want.