JS: let .gitignore decide which directories are output

[knutwannheden]

Motivation

ProjectParser has two discovery paths, and both end by filtering through the same glob list. On the git path that list is nearly redundant: candidates come from git ls-files plus git ls-files --others --exclude-standard, so .gitignore has already removed node_modules, dist, build, and coverage in essentially every project before a single pattern is evaluated.

Which means the default directory globs change the outcome only when they disagree with .gitignore — that is, only when the directory is tracked. And a tracked dist/ is a directory the project deliberately committed as source. So on the git path those patterns did nothing except in the one case where excluding was wrong. **/dist/** also matches at any depth, so src/dist/ was dropped along with it.

The file patterns are different in kind and do real work: *.min.js and *.bundle.js are frequently committed, and .gitignore will not identify them.

Summary

• On the git discovery path the defaults narrow to DEFAULT_TRACKED_EXCLUSIONS — dependency trees and minified bundles, the things that are sometimes committed but are never a project's own source. Everything else is left to .gitignore.
• node_modules stays excluded unconditionally even when committed, matching the existing hardcoded guard on the walk path.
• The walk path is unchanged and keeps the full DEFAULT_EXCLUSIONS, including when git discovery fails and falls back to it. Without git there is no .gitignore evaluation to lean on, so the globs remain the only defence.
• Caller-supplied exclusions keep replacing the defaults and keep applying on both paths — an explicit list still wins over git tracking.
• handle_parse_project forwarded request.exclusions ?? DEFAULT_EXCLUSIONS into the parser, so the parser could never tell "caller specified the defaults" from "caller specified nothing". It now forwards an absent value as absent.

Test plan

• New test/rpc/project-parser-exclusions.test.ts builds a real git repo whose dist/ is staged source and whose build/ is gitignored output. Four cases: .gitignore decides directories under git discovery; committed bundles and dependency trees stay excluded; caller exclusions override git tracking; the no-git walk still applies the full defaults.
• Two of the four failed before the change, for the reasons they name.
• npm test — 169 files passed, 1 skipped; 1931 tests passed, 24 skipped.
• npm run typecheck clean.

Note for reviewers

• This makes JavaScript and Python diverge slightly in mechanism, deliberately. Python's handle_parse_project has no git discovery — it is a raw os.walk — so Python: stop ParseProject pruning build/dist below the project root #8436 anchors build/dist to the project root instead. Root anchoring fixes the common src/build/ case without a git dependency; letting .gitignore decide is the better answer where the plumbing already exists, which on the Python side it does not.