shell func for cd'ing to top of git working copy

gcd.sh

# these implementations both take special care to keep `cd -` working correctly

# good way
gcd() {
	local TOP="`git rev-parse --show-cdup 2> /dev/null`" || return 1
	[ "$TOP" ] && cd "$TOP"
}

# old, dumb, bad way
gcd() {
	local OLDOLDPWD=$OLDPWD
	pushd . > /dev/null
	while : ; do
		if [ -d .git ] ; then
			OLDPWD="`dirs -l +1`"
			popd -n > /dev/null
			return
		fi
		[ "$PWD" = / ] && break
		cd ..
	done
	popd > /dev/null
	OLDPWD=$OLDOLDPWD
}