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.