support defining a simple dict of scheme format strings for get_version in pyproject.toml tool.setuptools_scm

[graingert]

trafficstars

for example:

# pyproject.toml

[tool.setuptools_scm.scheme]
no_distance_and_clean = "{tag}"
distance_and_clean = "{next_version}.dev{distance}+{scm_letter}{revision_hash}"
no_distance_and_not_clean = "{tag}+dYYYYMMDD"
distance_and_not_clean =  "{next_version}.dev{distance}+{scm_letter}{revision_hash}.dYYYYMMDD"

see also https://github.com/pypa/setuptools_scm/issues/418

[RonnyPfannschmidt]

after initial review of the current version scheme code vs this proposal i decided not to work on it in near future, im happy to review contirubtions

there has to be a distinction for the local scheme and the version scheme itself