What are the "variety of triggers" that run garbage collection on bitbucket cloud repos?

[jeremywelkley]

This FAQ states: 

The git gc command cleans up unnecessary files and optimizes the local repository. Bitbucket runs this operation on its hosted repositories automatically on a regular basis based on a variety of triggers. Locally you can run it at any time. Running it won't have any adverse affect on your repository.

I have a repo that bitbucket cloud support just performed an aggressive gc on and I would like to make sure I'm doing all I can to get the repo to auto clean itself.

[smf]

In general, we run `git gc` on every push to your repo (we don't have an option to run an aggressive version).