commitctx: move copy meta config reading in a dedicated function
The logic is non trivial, make it contained in a function is clearer. It also
unlock easy re-use of that logic without having the pass the value around.
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true