GNU/Hurd -- VFS-style union mount

by Sergiu Ivanov for GNU Project

Implement VFS-style union mounts in the Hurd. The idea is to provide a possibility to use VFS-style union mounts under the GNU/Hurd system via a special translator. This would allow for flexible usage of the main filesystem and a uniform access to different types of filesystems (which could be normal filesystem and virtual, ``hurdish'' filesystems). Also, implement some ``magic'' rules which would allow *controlled* union mounts; this could include translator manipulations.