metastore stores or restores metadata (owner, group, permissions, xattrs
and optionally mtime) for a filesystem tree.

See the manpage (metastore.1) for more details.

The file format of the .metastore files is as follows:

Data types
----------

CSTRING = NULL-terminated binary string

BSTRING(N) = binary string of length N

INT(N) = N byte integer in big endian byte order


File format
-----------
HEADER
N * ENTRY


HEADER format
-------------
BSTRING(10) - Magic header - "MeTaSt00r3"
BSTRING(8)  - Version - "\0\0\0\0\0\0\0\0" (currently)


ENTRY format
------------
CSTRING - Path (absolute or relative)
CSTRING - Owner (owner name, not uid)
CSTRING - Group (group name, not gid)

INT(8)  - Mtime (seconds)
INT(8)  - Mtime (nanoseconds)
INT(2)  - Mode (st_mode from struct stat st_mode AND 0177777,
                i.e. unix permissions and type of file)

INT(4)  - num_xattrs
FOR (i = 0; i < num_xattrs; i++) {
    CSTRING           - xattr name
    INT(4)            - xattrlen
    BSTRING(xattrlen) - xattr value
}