On: A one-line change decreased our build times by 99%

[pushrax]

I am fairly sure it uses thin packs during a clone usually. Though I checked the docs at https://www.git-scm.com/docs/shallow, and it says:

> There are some unfinished ends of the whole shallow business:

> - maybe we have to force non-thin packs when fetching into a shallow repo (ATM they are forced non-thin).