Provenance: https://github.com/p-ranav/argparse

Retrieved: https://github.com/p-ranav/argparse/blob/8dead89026466b3818e9c6b6b1d938600db39d8f/include/argparse/argparse.hpp
+ patch of https://github.com/p-ranav/argparse/pull/356 (FEATURE: multiple actions)
+ patch of https://github.com/p-ranav/argparse/pull/363 (Accept integer literals in store_into)

