Summary

Adds direct tests for hash_tree() so native fingerprint hashing is covered without going through the CLI or a native build.

Closes #91.

Motivation

#91 notes that tests/test_cli.py only checks artifact reuse when a fingerprint matches. There were no direct tests for the hashing contract: path+content stability, ignore lists, mtime independence, missing/empty roots, and single-file hashing.

Implementation

• New tests/project/test_fingerprint.py.
• Uses small tmp_path fixtures and compares hashes to each other rather than hard-coded digests.
• Covers ignored dirs (build, __pycache__, .git) and suffixes (.pyc, .DS_Store).
• Uses os.utime() to confirm mtime-only changes do not affect the digest.

Testing

This environment has Python 3.12; the project requires 3.13 (class Route[P: RouteParams = ...]), so uv run pytest / ./scripts/check.sh could not be run here.

The six cases were executed against hash_tree by loading src/pythonnative/project/fingerprint.py with a stub config module on Python 3.12. All assertions passed:

• identical trees under different roots / creation order
• byte change and rename change the hash
• mtime-only change does not
• ignored paths do not; a new source file does
• missing root and empty directory share the empty digest
• hashing a single file is path-root independent for the same basename+bytes