fix: Enhace black efficiently to skip directories listed in .gitignore

[Mr-Sunglasses]

Description

fix: #4405 Enhace black efficiently to skip directories listed in .gitignore

Checklist - did you ...

• Add an entry in CHANGES.md if necessary?
• Add / update tests if necessary?
• Add new / update outdated documentation?

[github-actions]

diff-shades reports zero changes comparing this PR (98264b7) to main (4b4ae43).

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[Mr-Sunglasses]

@JelleZijlstra I've added the test for this and now black is almost 2x faster when it have to ignore directories from .gitignore

A benchmark I've tested, with node_modules as ignored.

[Mr-Sunglasses]

Should we add a changelog entry as it's a simple but significant change?

[JelleZijlstra]

Thank you! I pushed a news entry.

[hauntsaninja]

Note this probably hurts perf in the normal case due to adding a bunch of new stats
This is more correct, but could be nice to rework things to use os.scandir and away from pathlib.Path