I added benchmarks to measure how fast the parallel remove_all code was
-- it turns out, about 3x slower than stdfs::remove_all. Since this was
the case, I removed all of the parallelism and rewrote it serially, and
ended up about 30% faster than stdfs::remove_all (in addition to
supporting symlinks).
In addition, I did the following three orthogonal changes:
- simplified the work queue, basing it on Billy O'Neal's idea
- Fix warnings on older versions of compilers in tests, by splitting
the pragmas out of pch.h.
- Ran clang-format on some files
In fixing up remove_all, the following changes were made:
- On Windows, regular symlinks and directory symlinks are distinct;
as an example, to remove directory symlinks (and junctions, for that
matter), one must use RemoveDirectory. Only on Windows, I added new
`file_type` and `file_status` types, with `file_type` including a new
`directory_symlink` enumerator, and `file_status` being exactly the
same as the old one except using the new `file_type`. On Unix, I
didn't make that change since they don't make a distinction.
- I added new `symlink_status` and `status` functions which use the
new `file_status` on Windows.
- I made `Filesystem::exists` call `fs::exists(status(p))`, as opposed
to the old version which called `stdfs::exists` directly.
- Added benchmarks to `vcpkg-test/files.cpp`. They test the
performance of `remove_all` on small directories (~20 files), with
symlinks and without, and on large directories (~2000 files), with
symlinks and without.
