Reference

All functions
build_pkg()	build various versions of a package
create_tagged_repo()	create a cranlike repo that contains the tagged package
git_url()	get the origin url
head_tag()	get the tag of the head (current commit)
insert_packages()	insert packages into a drat repo
new_cranlike_repo()	new cranlike repo will create a cranlike repo
skip_remaining_if_dev_tag()	skip remaining drone CI steps if tag is dev tag
tag_version()	add a git tag based on the pkg version