Fix Black formatting on Windows (issue #133)

[akaihola]

black.format_str() expects content to have Unix newlines. With Windows CRLF, it will give different results.

Make sure content newlines are converted from CRLF to LF before calling black.format_str(). Fixes #133.

• unit tests for new and changed code
• change log

[akaihola]

@martinRenou, I think I solved the issue of Black giving different results on Windows. It was because Darker would pass files with CRLF as newlines to black.format_str() as such, when Black expects UNIX newlines (LF).

The issue has been debugged and fixed in this PR.

Would you happen to have time for a review?

[sourcery-ai]

Sourcery Code Quality Report

✅  Merging this PR will increase code quality in the affected files by 0.23%.

Quality metrics	Before	After	Change
Complexity	1.55 ⭐	1.36 ⭐	-0.19 👍
Method Length	45.09 ⭐	46.51 ⭐	1.42 👎
Working memory	5.66 ⭐	5.64 ⭐	-0.02 👍
Quality	84.62% ⭐	84.85% ⭐	0.23% 👍

Other metrics	Before	After	Change
Lines	639	674	35

Changed files	Quality Before	Quality After	Quality Change
src/darker/black_diff.py	81.26% ⭐	79.91% ⭐	-1.35% 👎
src/darker/utils.py	84.17% ⭐	85.60% ⭐	1.43% 👍
src/darker/tests/test_black_diff.py	77.63% ⭐	80.69% ⭐	3.06% 👍
src/darker/tests/test_utils.py	87.73% ⭐	86.68% ⭐	-1.05% 👎

Here are some functions in these files that still need a tune-up:

File	Function	Complexity	Length	Working Memory	Quality	Recommendation
src/darker/tests/test_utils.py	test_textdocument_eq	0 ⭐	216 ⛔	7 🙂	63.89% 🙂	Try splitting into smaller methods
src/darker/tests/test_utils.py	test_textdocument_string_with_newline	0 ⭐	103 🙂	10 😞	68.60% 🙂	Extract out complex expressions
src/darker/utils.py	TextDocument.__repr__	3 ⭐	66 🙂	10 😞	70.98% 🙂	Extract out complex expressions
src/darker/utils.py	TextDocument.__init__	1 ⭐	41 ⭐	10 😞	76.94% ⭐	Extract out complex expressions

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The 👍 and 👎 indicate whether the quality has improved or gotten worse with this pull request.

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[akaihola]

Contributors are busy, all tests pass. I'll just trust my past self and merge this now.