0k-charms/precise/docker-builder/src/usr/lib/docker-updater/wrap-application

#!/bin/bash

orig=$0.diverted

if [ -z "$APP_LOCATION" ]; then
   echo "Error: APP_LOCATION was not defined."
   exit 1
fi

app=/srv/app
root=$app/root
changes=$app/changes/0000
mnt=$app/mnt

## All these should be in the root image
#mkdir -p $root $mnt
#mkdir -p "$(dirname "$APP_LOCATION")"

if [ -d "$changes" ]; then
    clean_all() {
        cd /
        mountpoint "$mnt" 2>/dev/null && umount "$mnt"
    }


    trap "clean_all" EXIT
    mount -t aufs -o br=$changes:$root -o udba=none  none "$mnt"
    if [ "$?" != 0 ]; then
        echo "Error: aufs mount failed."
        exit 1
    fi

    ln -sf "$mnt" "$APP_LOCATION"
else
    ln -sf "$root" "$APP_LOCATION"
fi

"$orig" "$@"