Update pants versioning to use python's packaging.version
Review Request #4200 - Created Aug. 31, 2016 and submitted
|benjyw, gmalmquist, jsirois, kwlzn, stuhood, zundel|
Change pants versioning to use python's packaging.version rather than semver. Python versioning doesn't
follow the semver spec. This change allows us to more closely follow the python spec. Specifically
python prefers versions of the form 1.2.0dev6 rather than 1.2.0-dev6. Semver does not allow for 1.2.0dev6.
This change is a follow up to changes to our naming conventions.
Ran ./build-support/bin/release.sh -n with both '1.2.0-dev6' and '1.2.0dev6'