crypt4gh-sqlite

Automating a bit more the sqlite file update

Fixing stx_btime, and trying to use pid as mnt_id, but seems ignored, or set elsewhere by libfuse and/or the kernel

Adding statx, if fuse >= 3.18

st_dev = getpid() and fixing the xattr zero-length value vs ENODATA

Adding the possibility to notify a parent, via a file descriptor, that everything went fine. Useful in combination with PAM and forking.