#!/bin/sh
#
# Perform a bind mount, copying existing files as we do so to ensure the
# overlaid path has the necessary content.

if [ $# -lt 2 ]; then
    echo >&2 "Usage: $0 spec mountpoint [OPTIONS]"
    exit 1
fi

spec=$1
mountpoint=$2

if [ $# -gt 2 ]; then
    options=$3
else
    options=
fi

[ -n "$options" ] && options=",$options"

mkdir -p "${spec%/*}"
if [ -d "$mountpoint" ]; then
    if [ ! -d "$spec" ]; then
        mkdir "$spec"
        cp -pPR "$mountpoint"/. "$spec/"
    fi
elif [ -f "$mountpoint" ]; then
    if [ ! -f "$spec" ]; then
        cp -pP "$mountpoint" "$spec"
    fi
fi

mount -o "bind$options" "$spec" "$mountpoint"