Use the installer.sh from the source tarball

This redesigns how update works. installer.sh now rebuild the package,
stops the old code and starts the new code. Importantly, it does not
download the new package, this is left to the caller. cloudron-setup
downloads the code and calls installer.sh of the downloaded code.
Same goes for updater.sh. This means that installer.sh itself is now
easily updatable.

Part of #152

src/scripts/update.sh

@@ -7,7 +7,6 @@ if [[ ${EUID} -ne 0 ]]; then
     exit 1
 fi
 
-readonly INSTALLER_PATH="/etc/installer.sh"
 readonly UPDATER_SERVICE="cloudron-updater"
 readonly DATA_FILE="/tmp/cloudron-update-data.json"
 
@@ -27,6 +26,22 @@ readonly data="${2}"
 echo "Updating Cloudron with ${sourceTarballUrl}"
 echo "${data}"
 
+# TODO: pre-download tarball
+box_src_tmp_dir=$(mktemp -dt box-src-XXXXXX)
+readonly installer_path="${box_src_tmp_dir}/scripts/installer.sh"
+echo "Downloading box code from ${sourceTarballUrl} to ${box_src_tmp_dir}"
+
+for try in `seq 1 10`; do
+    if curl -L "${sourceTarballUrl}" | tar -zxf - -C "${box_src_tmp_dir}"; then break; fi
+    echo "Failed to download source tarball, trying again"
+    sleep 5
+done
+
+if [[ ${try} -eq 10 ]]; then
+    echo "Release tarball download failed"
+    exit 3
+fi
+
 echo "=> reset service ${UPDATER_SERVICE} status in case it failed"
 if systemctl reset-failed "${UPDATER_SERVICE}"; then
     echo "=> service has failed earlier"
@@ -36,7 +51,7 @@ fi
 echo "${data}" > "${DATA_FILE}"
 
 echo "=> Run installer.sh as cloudron-updater.service"
-if ! systemd-run --unit "${UPDATER_SERVICE}" ${INSTALLER_PATH} --sourcetarballurl "${sourceTarballUrl}" --data-file "${DATA_FILE}"; then
+if ! systemd-run --unit "${UPDATER_SERVICE}" ${installer_path} --data-file "${DATA_FILE}"; then
     echo "Failed to install cloudron. See ${LOG_FILE} for details"
     exit 1
 fi