Only apply Black excludes to directories

[akaihola]

Unify exclusion behavior with Black: the exclude options from Black configuration only apply to directories listed on the command line, but not to files. Closes #104.

• diff .py.*.tmp against the corresponding .py file
• tests
• documentation
• change log

[sourcery-ai]

Sourcery Code Quality Report

❌  Merging this PR will decrease code quality in the affected files by 0.31%.

Quality metrics	Before	After	Change
Complexity	5.38 ⭐	5.40 ⭐	0.02 👎
Method Length	92.37 🙂	92.73 🙂	0.36 👎
Working memory	9.36 🙂	9.45 🙂	0.09 👎
Quality	65.55% 🙂	65.24% 🙂	-0.31% 👎

Other metrics	Before	After	Change
Lines	2555	2718	163

Changed files	Quality Before	Quality After	Quality Change
src/darker/main.py	41.47% 😞	42.24% 😞	0.77% 👍
src/darker/black_diff.py	73.94% 🙂	72.81% 🙂	-1.13% 👎
src/darker/git.py	77.55% ⭐	77.55% ⭐	0.00%
src/darker/linting.py	71.34% 🙂	71.34% 🙂	0.00%
src/darker/tests/test_black_diff.py	74.96% 🙂	72.16% 🙂	-2.80% 👎
src/darker/tests/test_command_line.py	70.67% 🙂	70.60% 🙂	-0.07% 👎
src/darker/tests/test_linting.py	76.31% ⭐	76.31% ⭐	0.00%
src/darker/tests/test_main.py	66.24% 🙂	66.40% 🙂	0.16% 👍

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

File	Function	Complexity	Length	Working Memory	Quality	Recommendation
src/darker/main.py	main	29 😞	396 ⛔	15 😞	19.85% ⛔	Refactor to reduce nesting. Try splitting into smaller methods. Extract out complex expressions
src/darker/tests/test_main.py	test_main	6 ⭐	434 ⛔	24 ⛔	30.58% 😞	Try splitting into smaller methods. Extract out complex expressions
src/darker/main.py	_reformat_single_file	11 🙂	216 ⛔	19 ⛔	35.04% 😞	Try splitting into smaller methods. Extract out complex expressions
src/darker/tests/test_command_line.py	test_parse_command_line	7 ⭐	736 ⛔	9 🙂	44.94% 😞	Try splitting into smaller methods
src/darker/tests/test_black_diff.py	test_filter_python_files	4 ⭐	242 ⛔	11 😞	49.82% 😞	Try splitting into smaller methods. Extract out complex expressions

Legend and Explanation

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• 🙂 good
• 😞 poor
• ⛔ very poor

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

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