Use ghc::filesystem as fill on older GCC (e.g. RoboRIO).
This can be removed once all GCC platforms have upgraded to 8.1 or later.
File open functionality has been retained from LLVM but moved to "fs" namespace
and tweaked for improved consistency with std::filesystem (e.g. error_code is
passed by reference instead of returned).
Also update WPILibC's Filesystem functions to return std::string.
This makes code easier to read and more consistent between C++ and Java.
Also update clang-format settings to always add a line break (even if no braces are used).
Previously this would list ALL /dev/video* devices. In recent versions of
Linux this leads to listing duplicate devices, as many USB cameras provide
both a video device and a metadata device, and only the video device can
actually be used for streaming.
std::scoped_lock was introduced in C++17 and is strictly better than
std::lock_guard as it supports locking any number of mutexes safely.
It's also easier to use than std::lock for locking multiple mutexes at
once.
This is primarily for use on Linux to get by-id or by-path device names.
This information is now part of UsbCameraInfo.
A new entry point was added to UsbCamera to get that camera's UsbCameraInfo.
The alternate paths are also returned in EnumerateUsbCameras.
This avoids a number of shutdown use-after-free races by controlling the
destruction order. It also is a prerequisite to making the internal
interfaces mockable for unit testing.
