Mongokit's migrations system stuff is complex and way confusing.
Here's something much simpler.


-  migrations are simple functions, iterated by number. You create
   them and register them with a decorator registering what "number"
   they are like so:

   @register\_migration(1) def ponies\_to\_unicorns(database):
   database['quadrapeds'].find( {'animal': 'pony'}).update{ {'$set':
   {'animal': 'unicorn'}})


or whatever else you need to do with that connection. The first and
only argument passed in (database) is a simple pymongo database
connection (**not** mongokit!). Otherwise, it's just a simple
python function. Do what you need to do.


-  current migration status is stored in the ['\_id'] =
   'mediagoblin' document of database['app\_metadata'] in the field
   ['migration\_number']
-  if no migrations have been run yet, migration\_number set to
   current max
-  otherwise all unrun migrations are run, and migration\_number
   updated after each migration finishes.

We should encourage people to install the appropriate libs so that
python-PIL is capable of saving and reading JPEG files. Update the
Hacking HOWTO and close this.

Comment links need to be changed so they don't expire when the
comment gets pushed to the next page by new comments.