git shortlog and http://codeimpossible.com/2011/12/16/Stupid-Git-Trick-getting-contributor-stats/

gitstats-by-author.sh

#!/bin/bash

sorted_commit_counts=`git shortlog -ns`
echo
echo "Commit Statistics by Authors"
echo "================================================"
echo
i=1

while read -r line; do
  commit_count=`echo "$line" | cut -f1`
  author_name=`echo "$line" | cut -f2`
  echo "$i. $author_name did $commit_count commits"
  git log --author="$author_name" --pretty=tformat: --numstat | \
  gawk '{ add += $1 ; subs += $2 ; loc += $1 - $2 } END \
  { printf "Added Lines: %s; Removed Lines: %s; Total Lines: %s\n",add,subs,loc }'
  echo
  i=$(($i + 1))
done <<< "$sorted_commit_counts"