Currently, we always sync on start-up, making start-up sloooow. We should have a command for it.

It should not be a migration (see #1137), because users can turn Gandalf on and off all the time.

Some pending points:

• are we going to really sync? (removing from gandalf whatever doesn't exist in tsuru)
• if we are not going to really sync, how do we detect that a user existed in tsuru and doesn't exist anymore, and it stil exists on Gandalf?

Should we just don't care and always create on Gandalf what exists in tsuru and never care about removing anything from Gandalf in the sync process? Or maybe add a --dedicated flag to indicate that the Gandalf instance is dedicated to tsuru, which means that tsuru can mirror its data in Gandalf, removing any non-matching users and repositories?

And from a philosophical point of view: is tsuru supposed to support a shared Gandalf? How do we handle conflicts in user or repositories name?

It's easy, but there's room for a decision, so I'm marking it as brainstorm as well.