git-subtree-dir: external/cli11
git-subtree-split: 13becaddb657eacd090537719a669d66d393b8b2

filesystem.cpp: Use reused path buffer for directory recursion. Use std::string_view for input directory name type, and std::string for returned filename type. Remove common_types.hpp.

git-subtree-dir: external/catch2
git-subtree-split: fbf03cd31c6a1c211fa85bd620defbdc4c2e37d0