Update to null safety, change list* apis (dart-lang/glob#39)

Also renames the list* apis on Glob to listFileSystem* and they now require a FileSystem object from package:file.

There is a new convenience import, package:glob/list_local_fs.dart which provides the old methods as extensions, and automatically passes a LocalFileSystem. Most migrations should be just importing this new file.

Note that when calling listFileSystem if the file system has changed then I chose to just throw away the old _ListTree. We could cache these by file system but I worry about memory leaks if people pass new instances of file systems repeatedly on the same glob.
12 files changed
tree: a2b87acbeac7e0fd286d33f25df37645c698bdae
  1. pkgs/