bashism free wrappers for cd and pwd for git-sh-setup

cd-and-pwd.sh

	pwd () {
		if test -z "${PWD#/[a-z]}"
		then
			#e.g. '/c' -> 'c:/'
			echo "${PWD#/}:/"
			return
		fi

		pwd_after_drive="${PWD#/[a-z]/}"
		if test "$pwd_after_drive" != "$PWD"
		then
			#e.g. '/c/dir' -> 'c:/dir'
			pwd_drive="${PWD%$pwd_after_drive}"
			pwd_drive="${pwd_drive%/}"
			pwd_drive="${pwd_drive#/}"
			echo "${pwd_drive}:/$pwd_after_drive"
			return
		fi

		#e.g. '//computer/share' -> '//computer/share'
		command pwd
	}

	cd () {
		if test -z "${1#[a-z]:}"
		then
			#e.g. 'cd c:' -> 'cd /c'
			command cd "/${1%:}"
			return
		fi

		if test -z "${1#[a-z]:/}"
		then
			#e.g. 'cd c:/' -> 'cd /c'
			command cd "/${1%:/}"
			return
		fi

		after_drive="${1#[a-z]:/}"
		if test "$after_drive" != "$1"
		then
			#e.g. 'cd c:/dir' -> '/c/dir'
			drive="${1%$after_drive}"
			drive="${drive%:/}"
			command cd "/${drive}/$after_drive"
			return
		fi

		#e.g. 'cd /c' -> 'cd /c'
		#e.g. 'cd /c/dir' -> 'cd /c/dir'
		#e.g. '//computer/share' -> '//computer/share'
		command cd "$1"
	}