sophisticated rsync wrapper

#!/bin/bash
LOCAL_BASE=${HOME}
REMOTE_BASE=${HOME}

REMOTE_HOST=10.1.2.3
REMOTE_PORT=22
REMOTE_USER=${LOGNAME}
REMOTE_KEY=${HOME}/.ssh/id_desktop

PUBLIC_HOST=192.0.2.2
PUBLIC_PORT=22
PUBLIC_USER=${LOGNAME}
PUBLIC_KEY=${HOME}/.ssh/id_server

TUNNEL_HOST=127.0.0.1
TUNNEL_PORT=2222

X=''
    X=${X}" .bash_aliases .bash_profile .bashrc .profile"
    X=${X}" .gdbinit .gitconfig .nanorc .screenrc .selected_editor"
    X=${X}" .ssh"
    X=${X}" .config/htop"
    X=${X}" .zsh_aliases* .zsh_env* .zshrc .oh-my-zsh"
    X=${X}" .config/google-chrome*"
    X=${X}" .icedove"
    X=${X}" .mozilla"
    X=${X}" .gnupg .password-store"
    X=${X}" .config/psi+ .cache/psi+ .local/share/psi+"
    X=${X}" .config/sublime-text-3"
    X=${X}" .config/vcsh .gitignore.d"
    X=${X}" .wireshark"
    X=${X}" .tsocks.conf"
    X=${X}" lib"
    X=${X}" prj"
    X=${X}" work"
RSYNC_PATH=${X}; unset X

###

TIMEOUT=5

DO_SSH="ssh -x -o ConnectTimeout=${TIMEOUT} -o Compression=no -o EscapeChar=none -o PreferredAuthentications=publickey"
RSYNC_RSH="${DO_SSH} -o IdentityFile=${REMOTE_KEY}"

X=''
    X=${X}" --archive --hard-links --specials --one-file-system --update --partial --progress --checksum"
    X=${X}" --modify-window=1"
    X=${X}" --compare-dest=${HOME}/.rsync_tmp"
    X=${X}" --verbose"
    X=${X}" --compress"
    X=${X}" --acls --xattrs"
RSYNC_OPT=${X}; unset X

D=/dev/null
SILENT="0<$D 1>$D 2>$D"; unset D
DAEMONIZE="${SILENT} &"

###

DIRECTION=
case "$1" in
u|U|up)   DIRECTION=u ;;
d|D|down) DIRECTION=d ;;
*) exit 1 ;;
esac
shift

echo 'probing remote side ...' 1>&2
eval ${DO_SSH} -o IdentityFile=${REMOTE_KEY} -N -T ${REMOTE_USER}@${REMOTE_HOST} ${DAEMONIZE}
TUNNEL_PID=$!
sleep $[TIMEOUT+1]

if eval ps -p ${TUNNEL_PID} ${SILENT}; then
    echo 'remote side available directly' 1>&2
    REMOTE_BASE=${REMOTE_USER}@${REMOTE_HOST}:${REMOTE_BASE}

    eval kill ${TUNNEL_PID} ${SILENT}
    TUNNEL_PID=''
else
    echo 'remote side unavailable; opening tunnel' 1>&2
    REMOTE_BASE=${REMOTE_USER}@${TUNNEL_HOST}:${REMOTE_BASE}

    RSYNC_RSH=${RSYNC_RSH}" -p ${TUNNEL_PORT}"

    eval ${DO_SSH} -o IdentityFile=${PUBLIC_KEY} -N -T -L ${TUNNEL_HOST}:${TUNNEL_PORT}:${REMOTE_HOST}:${REMOTE_PORT} ${PUBLIC_USER}@${PUBLIC_HOST} ${DAEMONIZE}
    TUNNEL_PID=$!
    sleep $[TIMEOUT+1]

    if ! eval ps -p ${TUNNEL_PID} ${SILENT}; then
        echo 'tunnel provider is unavailable' 1>&2
        exit 1
    fi
fi

Z=
if [ -z "$*" ]; then
    Z=${RSYNC_PATH[@]}
else
    Z=$@
    LOCAL_BASE=${PWD}
fi

SRC=
DST=
case "${DIRECTION}" in
u)
    SRC=${LOCAL_BASE}
    DST=${REMOTE_BASE}
;;
d)
    SRC=${REMOTE_BASE}
    DST=${LOCAL_BASE}
;;
esac

###

export RSYNC_RSH

echo 'begin transfer' 1>&2
echo " \`${SRC}' -> \`${DST}'" 1>&2

for i in ${Z}; do
    D=$(dirname "$i")
    if [ "$D" = '.' ]
    then D=${DST}
    else D=${DST}/$D
    fi

    echo "$i::" 1>&2
    rsync ${RSYNC_OPT} "${SRC}/$i" "${D}"
    echo 1>&2
    echo 1>&2
done

echo 'transfer is done' 1>&2

if [ -n "${TUNNEL_PID}" ]; then
    echo 'closing tunnel' 1>&2
    eval kill ${TUNNEL_PID} ${SILENT}
fi