Force pushing a commit to a theme repository used to break the updater,
because the system was not able to count the commits behind the old and
new version. This operation failed because a force push deleted the old
commits.
The user was prompted with a simple "500 server error" message.
Themes marked for auto update will be automatically updated when
Discourse is updated. This is triggered by discourse_docker or
docker_manager running Rake task 'themes:update'.
We were trying to observe a non-ember object which is undefined
behavior and was leaking to odd bugs. This replaces the `filter` object
with an Ember Object and things seem to work.
