If the git tag is a valid calendar version string, the system provides the tag as a calendar version string.
DRONE_CALVER=19.1.0-beta.20190318
The calendar version string is also available in the following formats:
DRONE_CALVER_SHORT=19.1.0
DRONE_CALVER_MAJOR_MINOR=19.1
DRONE_CALVER_MAJOR=19
DRONE_CALVER_MINOR=1
DRONE_CALVER_MICRO=0
DRONE_CALVER_MODIFIER=beta.20190318