libcmdline

This is a build2 package for the cmdline C++ library. It provides a header-only command line parser with typed options, generated usage text, and optional value constraints.

This package's cmdline.h is a backwards-compatible superset of upstream: alongside MSVC portability fixes, it adds a few bug fixes (swallowed error messages, an empty-vector edge case, a Windows macro clash) and some new opt-in parsing capabilities (stop-at-rest passthrough, a header/footer, and parsing argv-like lists without a program name). Everything is additive, so code written against vanilla tanakh/cmdline keeps compiling and behaving the same.