This is redundant (but harmless) on a Posix system, but it fills a missing
puzzle piece on Windows. The point of fsyspath is to be able to interchange
freely between fsyspath and std::string. Existing fsyspath could be
constructed and assigned from std::string, and we could explicitly call its
string() method to get a std::string, but an implicit fsyspath-to-string
conversion that worked on Posix would trip us up on Windows. Fix that.
(cherry picked from commit fbeff6d8052d4b614a0a2c8ebaf35b45379ab578)
Our std::strings are UTF-8 encoded, so conversion from std::string to
std::filesystem::path must use UTF-8 decoding. The native Windows
std::filesystem::path constructor and assignment operator accepting
std::string use "native narrow encoding," which mangles path strings
containing UTF-8 encoded non-ASCII characters.
fsyspath's std::string constructor and assignment operator explicitly engage
std::filesystem::u8path() to handle encoding. u8path() is deprecated in C++20,
but once we adapt fsyspath's conversion to C++20 conventions, consuming code
need not be modified.
(cherry picked from commit e399b02e3306a249cb161f07cac578d3f2617bab)
Andrey Lihatskiy