Revert "reducing the depth of the git checkout"
Revert "reducing the depth of the git checkout"

This reverts commit 5aaabc6b35988a4c88b1d6fc2e36e44874c39b7e.

stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math,stan-dev/math