Follow-up of this so-question: if I have a shallow clone, how to fetch all older commits to make it a full clone?
EDIT: git fetch --unshallow
now is an option (thanks Jack O'Connor).
You can run git fetch --depth=2147483647
From the docs on shallow:
The special depth 2147483647 (or 0x7fffffff, the largest positive number a signed 32-bit integer can contain) means infinite depth.