Feature: Allow shadowing cipherdir with mountpoint

[Atrate]

It would be nice if gocryptfs allowed shadowing the cipherdir with its decrypted mountpoint, like ecryptfs.

I am not knowledgeable enough as to whether FUSE supports it or whether it's possible to do without superuser rights/a kernel module, so I'm just throwing the idea here.

Current behavior:

> gocryptfs /tmp/tmp.2CrICJxW7V/test /tmp/tmp.2CrICJxW7V/test
Mountpoint "/tmp/tmp.2CrICJxW7V/test" would shadow cipherdir "/tmp/tmp.2CrICJxW7V/test", this is not supported

[rfjakob]

Hi, this is theoretically possible, but isn't it just super confusing?