Is it possible to download and apply Debian testing snapshot image deltas?

I realised that there are constantly new Debian testing snapshosts[1]. I would like to know where I can see the changelog of these snapshots.

Also, I would like to know how to apply those deltas to an existing image that I have. Is it it a matter of just $ apt upgrade? Thanks.

ā€“ Luther

[1] http://elinux.org/Beagleboard:BeagleBoneBlack_Debian#Jessie_Snapshot_lxqt