Allow for merging with json-patch

[Joshua Harlow]

It would be pretty nice to allow for merging using the json patch specification.

https://tools.ietf.org/html/rfc6902 (https://tools.ietf.org/html/rfc6902#page-4)

Said specification provides a common way to add/remove/delete when patching:

'''
   This format is also potentially useful in other cases in which it is
   necessary to make partial updates to a JSON document or to a data
   structure that has similar constraints (i.e., they can be serialized
   as an object or an array using the JSON grammar).
'''

Since cloud-inits cloud-config is yaml (but could just as easily be json), the above seems pretty applicable to the type of updates (merging) that cloud-init performs. To start it might be neat to allow for a new mime-type that #json-patch where these types of merging operations happen.

https://pypi.python.org/pypi/jsonpatch/0.6 exists and seems like its being actively developed and it will likely make applying the specification much easier to do.

[Scott Moser (smoser)]

This was fixed in trunk at revno 842.

[Scott Moser (smoser)]

fixed in 0.7.3

[James Falcon (falcojr)]

Tracked in Github Issues as https://github.com/canonical/cloud-init/issues/2377