Use git repo data (latest tag, current commit hash, etc)
for building a version number according PEP 440.

Features:

Can be installed & configured through both setup.py and PEP 518's pyproject.toml
Does not require to change source code of the project
Tag-, file-, and callback-based versioning schemas are supported
Templates for tag, dev and dirty versions are separated
Templates support a lot of substitutions including git and environment
information
Well-documented
