Implement filesystem NB comments, relative paths, and related issues.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/libcxx/test/std/experimental/filesystem/class.path/path.itr/iterator.pass.cpp b/libcxx/test/std/experimental/filesystem/class.path/path.itr/iterator.pass.cpp
index e5b3c848255..0ea672bdf1e 100644
--- a/libcxx/test/std/experimental/filesystem/class.path/path.itr/iterator.pass.cpp
+++ b/libcxx/test/std/experimental/filesystem/class.path/path.itr/iterator.pass.cpp
@@ -83,14 +83,14 @@ void checkBeginEndBasic() {
   }
   {
     path p("//root_name//first_dir////second_dir");
-    const path expect[] = {"//root_name", "/", "first_dir", "second_dir"};
+    const path expect[] = {"/", "root_name", "first_dir", "second_dir"};
     assert(checkCollectionsEqual(p.begin(), p.end(), std::begin(expect), std::end(expect)));
     assert(checkCollectionsEqualBackwards(p.begin(), p.end(), std::begin(expect), std::end(expect)));
 
   }
   {
     path p("////foo/bar/baz///");
-    const path expect[] = {"/", "foo", "bar", "baz", "."};
+    const path expect[] = {"/", "foo", "bar", "baz", ""};
     assert(checkCollectionsEqual(p.begin(), p.end(), std::begin(expect), std::end(expect)));
     assert(checkCollectionsEqualBackwards(p.begin(), p.end(), std::begin(expect), std::end(expect)));