It has always been a weird thing that dib is a python package, but
is totally driven by the disk-image-create script. It creates this
strange division that is hard to explain.
This moves disk-image-create to a regular python entry-point
Currently, this simply exec()s the original disk-image-create script.
However, we now have a (private) interface between disk-image-create
written in python and the driver shell script. Here's some things we
could do, for example:
* Argument parsing is generally nicer in Python, and then end result
is mostly just setting environment variables to flag different things
in the shell script. I could see us moving the argument-parsing into
diskimage_builder.disk_image_create:main() and just setting things in
os.environ before the exec()).
* I7092e1845942f249175933d67ab121188f3511fd sets IMAGE_ELEMENT_YAML in
disk-image-create by calling-back to element-info. We can just call
element_dependencies.find_all_elements() in here an export is to
os.environ before disk-image-create starts.
* remove need for ramdisk-image-create symlink by just exporting
IS_RAMDISK based on sys.argv[1] value
* you could even unit test some of this :)
Change-Id: I69ca3d26fede0506a6353c077c69f735c8d84d28
