Git diff with line numbers

diff.sh

git diff HEAD^ HEAD | awk '
/^@@/ {
    gsub(/@@|\+|\-|@@/, "", $0);
    split($1, old, ",")
    split($2, new, ",")
    old_line = old[1]
    new_line = new[1]
    next
}
{ 
    if ($0 ~ /^(---|\+\+\+)|diff|index/) {
        print $0;
    }
    else if($0 ~ /^-/) {
        printf "-%4s %s\n", old_line, substr($0,2);
        old_line++;
    } else if($0 ~ /^\+/) {
        printf "+%4s %s\n", new_line, substr($0,2);
        new_line++;
    } else {
        print "    ", $0;
        old_line++;
        new_line++;
    }
}' | grep -e "^[-+]" | grep offset