makefile: add a install-chg option
This is done as a gratuitous improvement on the way to add makefile entry to
build and install rhg.
It seems saner to have equivalent entry for chg too.
Differential Revision: https://phab.mercurial-scm.org/D10192
[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true