Writable directories in /var/snap?

[Otfried Cheong]

Hello,

I'm trying to create my first snap, and have a first question:

When a snap is installed (say hello-world), the system creates two data
directories, /var/snap/hello-world/<revision> and
/var/snap/hello-world/common.   

Apparently these are meant for the snap when it needs writable storage,
but both directories are owned by root, and I haven't found any way to
write to them, either from inside the snap or outside, whether
installing in --devmode or not.

Cheers,
 Otfried