a shell script help me to view code diff on my jailbreak iPad. View more detail on [View code with your iPad and git](http://puttin.github.io/2013/04/18/view-code-with-your-ipad-and-git/)

genDiff.sh

#!/bin/bash

#default: diff last 2 commit
count=2
#default: check next commit
upordown=1

while getopts "u:d:" arg
do
    case $arg in
         u)
            #echo "u's arg:$OPTARG"
            count=$OPTARG
            upordown=1
            ;;
         d)
            count=$OPTARG
            upordown=-1
            ;;
         ?)
        echo "unkonw argument"
        exit 1
        ;;
    esac
done

#project dir
cd ~/Textastic/Documents/ViewDeck;
#cd ~/Repo/PWLoadMoreTableFooter

#get current_commit
git clean -dxf
#git checkout -b viewdiff #just in case there is no "viewdiff" branch
git checkout viewdiff
current_commit=$(git log --pretty=format:%H -1)

#get destination commit
git clean -dxf
git checkout master
line=$(git log --pretty=format:%H|grep -n "$current_commit"|cut -d ":" -f 1)
destination=$[$line-$[$upordown*$[$count-1]]]
destination_commit=$(git log --pretty=format:%H|sed -n "$destination"p)
#echo "line:$line destination:$destination"

git clean -dxf
git checkout viewdiff
git reset --hard $destination_commit
echo "current_commit:$current_commit"
echo "destination_commit:$destination_commit"
FILE="../result.diff"
rm $FILE
if [[ upordown -eq 1 ]]; then
    echo "up"
	git diff $current_commit $destination_commit > $FILE #git version:1.5.6 don't have -W option
	#git diff -W $current_commit $destination_commit > $FILE
elif [[ upordown -eq -1 ]]; then
	echo "down"
	git diff $destination_commit $current_commit > $FILE
	#git diff -W $destination_commit $current_commit > $FILE
else
	echo "ERROR!"
fi