Check git for updates.

git_check.sh

#!/bin/sh
git remote update
local=$(git rev-list --max-count=1 master)
origin=$(git rev-list --max-count=1 origin/master)

if [ "$local" != "$origin" ];
then
    git pull origin master
    echo "Lets build it :)"
    sh -ex ./build_ota.sh
else
    echo "No changes :("
fi