For those of us not on BSD: git ls-files -z | xargs -0 -n1 -E'\n' git blame --date short -wCMcp | perl -pe 's/^.*?\((.*?) +\d{4}-\d{2}-\d{2} +\d+\).*/\1/'

For those of us not on BSD: git ls-files -z | xargs -0 -n1 -E'\n' git blame --date short -wCMcp | perl -pe 's/^.*?\((.*?) +\d{4}-\d{2}-\d{2} +\d+\).*/\1/' | sort | uniq -c | sort -rn