ruby/tool/git-refresh

#!/bin/sh
set -e

quiet=
branch=

until [ $# = 0 ]; do
    case "$1" in
	--) shift; break;;
	-C|--directory) shift; cd "$1";;
	-C*) cd `expr "$1" : '-C\(.*\)'`;;
	--directory=*) cd `expr "$1" : '[^=]*=\(.*\)'`;;
	-q) quiet=1;;
	-b|--branch) shift; branch="$1";;
	-b*) branch=`expr "$1" : '-b\(.*\)'`;;
	--branch=*) branch=`expr "$1" : '[^=]*=\(.*\)'`;;
	-*) echo "unknown option: $1" 1>&2; exit 1;;
	*) break;;
    esac
    shift
done

url="$1"
dir="$2"
shift 2
if [ -d "$dir" ]; then
    echo updating `expr "$dir" : '*/\(.*\)'` ...
    [ $quiet ] || set -x
    cd "$dir"
    git fetch "$@"
    exec git checkout ${branch:+"$branch"} "$@"
else
    echo retrieving `expr "$dir" : '*/\(.*\)'` ...
    [ $quiet ] || set -x
    exec git clone "$url" "$dir" "$@"
fi