delta-find: add a simple safeguard to prevent bad non-general-delta This make it easier to catch request to build delta that does not make sense in the general delta world. It seems better to raise a programming error than to corrupt the repository.

[build-system]
requires = ["setuptools", "wheel"]

[tool.black]
line-length = 80
exclude = '''
build/
| wheelhouse/
| dist/
| packages/
| \.hg/
| \.mypy_cache/
| \.venv/
| mercurial/thirdparty/
'''
skip-string-normalization = true
quiet = true