gdiff

#!/bin/bash
# Show difference between commits
# Usage: gdiff -n 1 <filename>
usage() {
    echo "Usage: $0 -n|--commits num <filename>"
    echo " Show git difference between <num> commits "
    exit 1
}

ARGV=`getopt -a -o n: -l commits: -- "$@"`
[ $? -ne 0 ] && usage
eval set -- "${ARGV}"
while true
do
    case "$1" in
        -n|--commits)
            if [[ $2 =~ ^~?[0-9]+$ ]]; then
                num=$2
            else
                echo "Accept integter ONLY for commits numbers"
                exit 1
            fi
            shift
            ;;
        --)
            shift
            break
            ;;
    esac
    shift
done

i=1
compares=""
for commit in `git log --reverse -n ${num} ${1} |grep ^commit|awk 'NR==1{print $2}; END{if (NR>1) {print $2;}}'`
do
    if [ ${i} -eq 1 ]; then
        compares="${commit}"
        i=$(((++i)))
    else
        if [ ! -z ${commit} ]; then
            compares="${compares}..${commit}"
        else
            compares="${compares}..HEAD"
        fi
        i=$(((++i)))
    fi
done
if [ ${i} -eq 2 ]; then
    compares="${compares}..HEAD"
fi

git diff ${compares} ${1}