Black not using global config when running on internal packages

[ronyis]

Running black tool locally, on internal packages which include a pyproject.toml file, do not use the global config defined in the main pyproject.toml (under root).

This issue was introduced since #2884, after adding pyproject.toml to all packages, which do not include black config.

When black is executed over files in the root directory, it does use the global config, since it ever uses only a single pyproject.toml each run (see Black lookup-hierarchy). This is still the case when running tox -e lint.

This issue makes it hard to execute black on changed files during development.
A possible workaround is to add a command arg black --config pyproject.toml to make black use the root config file. Though this is a bit cumbersome, and not documented.

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Steps to reproduce
Run .tox/lint/bin/black ./opentelemetry-sdk --check (on a clean repo clone).

What is the expected behavior?
No files would be reformatted.

What is the actual behavior?

Oh no! 💥 💔 💥
49 files would be reformatted, 31 files would be left unchanged.

[ofek]

In our monorepos we also set the config path https://github.com/DataDog/integrations-core/blob/0b2db55128cfacc7406cff9c18027a33e7d1f0a7/datadog_checks_dev/datadog_checks/dev/plugin/hatch/environment_collector.py#L106-L108

[ofek]

open-telemetry/opentelemetry-python-contrib#1322

[ronyis]

Do you think it's needed to update docs on how to properly run it? (@ofek)
Maybe CONTRIBUTING.md#development is a good place for that

[ofek]

This

opentelemetry-python/scripts/eachdist.py

Line 516 in 725c580

def lint_args(args):

needs open-telemetry/opentelemetry-python-contrib#1322

[srikanthccv]

This was addressed in #2929. Please re-open if it's not fixed.