This is a fairly large patch that implements all of the filesystem NB comments
and the relative paths changes (ex. adding weakly_canonical). These issues
and papers are all interrelated so their implementation couldn't be split up
nicely.
This patch upgrades <experimental/filesystem> to match the C++17 spec and not
the published experimental TS spec. Some of the changes in this patch are both
API and ABI breaking, however libc++ makes no guarantee about stability for
experimental implementations.
The major changes in this patch are:
* Implement NB comments for filesystem (P0492R2), including:
* Implement `perm_options` enum as part of NB comments, and update the
`permissions` function to match.
* Implement changes to `remove_filename` and `replace_filename`
* Implement changes to `path::stem()` and `path::extension()` which support
splitting examples like `.profile`.
* Change path iteration to return an empty path instead of '.' for trailing
separators.
* Change `operator/=` to handle absolute paths on the RHS.
* Change `absolute` to no longer accept a current path argument.
* Implement relative paths according to NB comments (P0219r1)
* Combine `path.cpp` and `operations.cpp` since some path functions require
access to the operations internals, and some fs operations require access
to the path parser.
llvm-svn: 329028
Eric Fiselier