check your responsibility

blamerate

#!/bin/sh

if [ $# -eq 2 ]
then
 i=$2
else
 i=`whoami`
fi

declare -i mine=`git blame $1 | grep -i $i | wc -l`
declare -i total=`cat $1 | wc -l`
declare -i rate=$mine*100/$total

echo $rate'%'

blamerate /path/to/file author