fix(backend): skip symlinks instead of refusing the whole repository

[parthrohit22]

Closes #447.

The problem

One symlink anywhere in a checkout rejected the entire import:

{"code": "validation_error",
 "message": "Repository contains a symlink, which is not supported.",
 "details": {"path": "/tests/certs/valid/ca"}}

That's psf/requests — a link in a TLS test fixture, and one of the most widely read Python repositories in existence could not be opened at all. Symlinks are ordinary: test fixtures, monorepo package links, a docs path pointing at a shared file.

The change

The parser records each link and steps over it.

The security posture strengthens rather than weakens. The original guard existed because is_dir(), is_file() and stat() all follow symlinks, so walking one would catalogue whatever it points at — including host filesystem content reached through a link escaping the checkout. Skipping never resolves the link at all, so that content is unreachable by construction rather than by a check. The link's own target is deliberately never resolved or reported.

It also brings the tree walk in line with what the same parser already does for metadata — _safe_file has always treated a symlinked manifest as "simply absent rather than failing the whole import". The tree walk was the only place that refused.

RepositoryMeta gains skippedSymlinks, so the omission is visible rather than silent and a reader can tell not followed from not present — the same honest-limits posture the review layer takes everywhere else.

Tests

The existing security tests are kept and made stricter. They previously asserted an exception was raised; they now assert the escape is unreachable — the link is absent from the tree, and nothing behind it appears anywhere in the response:

assert "/evil_link" not in paths
assert not any("secret.txt" in path for path in paths), "host content leaked through a symlink"
assert paths == ["/README.md"]
assert meta.skipped_symlinks == ["/evil_link"]

Plus new coverage for an internal link (not a second copy of its target), and for the max_file_count preflight walk (a skipped link counts for nothing against the budget).

Verified against the repository that motivated it

psf/requests, live import:

imported  : requests | 128 files | Python
skipped symlinks: ['/tests/certs/mtls/client/ca', '/tests/certs/valid/ca']
analysis  : completed
snapshot  : snap_6020973412af48aa8  sha256:470cc2dccc28a3c7eff

Contract

RepositoryMeta gained a field, so the frontend contract is regenerated and five test fixtures that build meta by hand are completed. Backend suite green, frontend 457/457, ruff and eslint clean.

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Project	Deployment	Actions	Updated
partha-frontend	Ready	Preview	Sep 11, 2026 4:42pm UTC