The current postfix conversions are:
CURRENT / STABLE / PRERELEASE, 12.x-CURRENT becomes 12.snapYYYYMMDDhhmmss
ALPHAx -> .ax, so 11.3-ALPHA1 becomes 11.3.a1
BETAx -> .bx, so 12.1-BETA2 becomes 12.1.b2
RCx -> .rcx, so 13.0-RC3 becomes 13.0.rc3
RELEASE -> (nothing), so 12.1-RELEASE becomes 12.1
RELEASE-pX -> pX, so 12.1-RELEASE-p1 becomes 12.1p1
Note that for development branches we will start to drop the minor version
component entirely, which more closely matches how these branches are
physically named (stable/NN).
snap is a new prefix that will be introduced in [0], which is simply a more
verbose version of the current ".s" used.
[0] https://github.com/freebsd/pkg/pull/1929
Submitted by: rene (original, original version)