GitLineCounter.sh

#!/usr/local/bin/bash
# For when you need to count lines based on file extensions so you can accurately see the difference
# You must be on a current branch before executing this
# Pass your author name as the input i.e. `./GitLineCounter.sh MyName`

git log --numstat --oneline --author="$1" --format= > file
declare -A addedLines=()
declare -A removedLines=()

while read line; do
  if ! [ -z "${line##*=>*}" ]; then
    read added removed filepath <<<"$line"
    filename=$(basename -- "$filepath")
    extension="${filename##*.}"
    if [ "$added" != "-" ]; then
      if [ -z "${addedLines[$extension]}" ]; then
        addedLines[$extension]=$added
      else
        addedLines[$extension]=${addedLines[$extension]}+$added
      fi
    fi
    if [ "$removed" != "-" ]; then
      if [ -z "${removedLines[$extension]}" ]; then
        removedLines[$extension]=$removed
      else
        removedLines[$extension]=${removedLines[$extension]}+$removed
      fi
    fi
  fi
done < file

for i in "${!addedLines[@]}"
do
  echo "*.$i: +$(("${addedLines[$i]}")) -$(("${removedLines[$i]}"))"
done