The swift man page on Linux and macOS is essentially the same, providing only a starting point. Running 'swift -help' gives a listing of options, but leaves out much detail, which is no surprise.
But I've been looking for some hours and still haven't found anything explaining the options in depth. In fact, running grep on the source tree from the top level reveals that the only place where options are mentioned are in the source file ToolChains.cpp, which is what parses the options.
It seems like they are almost entirely undocumented.
Can someone tell me where this information is?