% gem install semver

% semver init
% semver tag                # => v0.0.0
% semver inc minor          # => v0.1.0
% git tag -a `semver tag`
% say 'that was easy'

require 'semver'
v = SemVer.find
v.major                     # => "0"
v.major += 1
v.major                     # => "1"
v.format "%M.%m.%p"         # => "1.1.0"
v.to_s                      # => "v1.1.0"
v.save

% git config --global alias.semtag '!git tag -a $(semver tag) -m "tagging $(semver tag)"'