Ok, here's a better test:
```
git clone ${target_repo} --branch ${target_branch} --single-branch target-size-clone
target_size=`du -s target-size-clone | sed -e "s/\s.*//"`
git clone ${source_repo} --branch ${source_branch} --single-branch source-size-clone
source_size=`du -s source-size-clone | sed -e "s/\s.*//"`
```
..but I'm not sure the best place to get the repo and branch variables needed.