#!/bin/sh
# difflines -- show lines added/removed across a git range
# Usage: difflines [since]
#        difflines HEAD~10
#        difflines main

since="${1:-HEAD~1}"
added=$(git diff "$since" --numstat | awk '{s+=$1}END{print s+0}')
removed=$(git diff "$since" --numstat | awk '{s+=$2}END{print s+0}')
files=$(git diff "$since" --numstat | wc -l)

printf "+%s -%s across %s files (since %s)\n" "$added" "$removed" "$files" "$since"