setup environment/directories for app data

[Michael Vogt]

The actual pathes that are going to be used is right now under discussion.

We need to create the path in /var/lib/apps/$pkg/$version and provide the environment SNAPP_APP_DATA_PATH in systemd units and do the same for the user directories.

[Alexander Sack (asac)]

guess bug 1400368 might be part of this general issue.

[Martin Pitt (pitti)]

Repeating the important bits from bug 1400368 here:

SNAPP_APP_DATA_PATH=/var/lib//apps/ros-tutorial/0.2
SNAPP_APP_USER_DATA_PATH=/home/ubuntu//apps/ros-tutorial/0.2

$SNAPP_APP_DATA_PATH sounds fine, but is root:root, so cannot be written to by the app. $SNAPP_APP_USER_DATA_PATH sounds like the intended place, but the directory doesn't exist (which the description already mentions), but more importantly: it is version specific, so every upgrade of an app would suddenly lose all of its config/data. So this isn't currently appropriate at all.

[Michael Vogt (mvo)]

The data dirs are created and the data is copied on upgrade with current snappy.