Describe how to build file system (like gen_init_cpio.c)

[mhx]

Per issue #6:

The above could be quite simple to implement, however an even more useful option would be something like this:

• in the Linux kernel there is a small tool gen_init_cpio.c (https://github.com/torvalds/linux/blob/master/usr/gen_init_cpio.c#L452) which takes a file describing how an cpio archive (to be used for the initramfs) should be created (see the source code at the hinted line for the file syntax); thus in addition to the previous feature of file-lists, such a "file-system" descriptor would allow one to create (without root credentials on his machine) a file-system with any layout;
• as an extension to the above, perhaps JSON would be a better choice; :)