v6.4.2
* fix #671 : NoReturn is not avaliable in painfully dead python 3.6
v6.4.1
* fix regression #669: restore get_version signature
* fix #668: harden the selftest for distribution extras
v6.4.0
* compatibility adjustments for setuptools >58
* only put minimal setuptools version into toml extra to warn people with old strict pins
* coorectly handle hg-git self-use
* better mercurial detection
* modernize packaging setup
* python 3.10 support
* better handling of setuptools install command deprecation
* consider pyproject.tomls when running as command
* use list in git describe command to avoid shell expansions while supporting both windows and posix
* add --strip-dev flag to python -m setuptools_scm to print the next guessed version cleanly
* ensure no-guess-dev will fail on bad tags instead of generating invalid versions
* ensure we use utc everywhere to avoid confusion
