rust-index: simplification in find_gca_candidates()
`parent_seen` can be made a mutable ref, making this part more obvious,
not needing to be commented so much.
The micro-optimization of avoiding the union if `parent_seen` and
`current_seen` agree is pushed down in the `union()` method of the
fast, `u64` based bit set implementation (in case it matters).
[build-system]
requires = ["setuptools", "wheel"]
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true