[$] Distributing filesystem images and updates with casync

Recently, Lennart Poettering announceda new tool called casync for efficiently distributing filesystem and diskimages. Deployment of virtual machines or containers often requires suchan image to be distributed for them. These images typically contain mostor all of an entire operating system and its requisite data files; they canbe quite large. The images also often need updates, which can take upconsiderable bandwidth depending on how efficient the update mechanismis. Poettering developed casync as an efficient tool for distributing suchfilesystem images, as well as for their updates.