Support for user mount options

[stephanritscher]

Is your feature request related to a problem? Please describe.
gocryptfs doesn't support multiple passwords for the same directory except for using copies of the config file. However only the config file with the default config file CIPHERDIR/gocryptfs.conf currently can be used with gocryptfs.

Describe the solution you'd like
Please add a per-vault optional property user mount options (or similar) where any additional mount options could be specified (e.g. in mount-compatible comma separated syntax).

Additional context
I could imagine more use cases with gocryptfs:

• Specifying reverse option to get an encrypted view of a plain text directory, possibly with exclude patterns
• Specifying security flags (suid/nosuid, exec/noexec, dev/nodev)
• Mounting over nonempty directories
• Specifying sharedstorage in multi-user shared directories or on synced/cloud directories

I guess that also the other backends would benefit.

[mpobaschnig]

Okay, this is quite difficult to implement properly without suddenly living in the wild west. It would be better if we'd create a list of options that make sense for the general user and which can be set in the vault settings.

[Acumane]

On the subject of options, allow_other is available in both gocryptfs and CryFS. Perhaps not a default, but I wish it were exposed in Vaults

[BlauerHunger]

for gocryptfs, -noprealloc would also be nice to manually set through Vaults.

Use case: There are filesystems on which gocryptfs doesn't automatically enable it, but where it may be beneficial for performance depending on the backing storage, for example with virtiofs backed by btrfs.