I was chatting with siris on Discord about an issue he was having and he asked me how to 'roll back' meta-repo to an earlier version so he could try installing an older version of polkit.

I gave him the steps to do it manually, but I realized that it would be far easier and quite cool if ego had this functionality built-in.

I can see two potential features:

1. roll back to an earlier version of meta-repo that you have locally.
2. sync an entirely new meta-repo using a specific timestamp.