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

This reverts commit d7fafd38b400a367e766238db175732a5342dae1.

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