Create Archived Revision of File Changes

archived_revision_of_file_changes.sh

#!/usr/bin/env bash

set -eu

# ----------------------------------------
# Variables
# ----------------------------------------
INSTALL_DIR="/var/www/html"
SHARED_DIR="/var/www/shared/html"
TIMESTAMP=$(date -u +"%Y%m%dT%H%M%SZ")

# ----------------------------------------
# Validate local.xml 
# ----------------------------------------
# check for existence and create archived revision if changed

# Make sure archived_revisions directory exists
[[ ! -d ${SHARED_DIR}/app/etc/archived_revisions ]] && mkdir -p ${SHARED_DIR}/app/etc/archived_revisions

# Make sure source is a real file and not a symlink
[[ ! -f ${INSTALL_DIR}/app/etc/local.xml ]] || [[ -L ${INSTALL_DIR}/app/etc/local.xml ]] && echo 1>&2 "ERROR: local.xml does not appear to be a normal file!" && exit 1

# Check for differences
# Compute digest hash of each file contents for comparing
SOURCE_DIGEST=$(cat ${INSTALL_DIR}/app/etc/local.xml | openssl dgst -sha256 -binary | xxd -p -c 256)
LATEST_REV_DIGEST=$(cat ${SHARED_DIR}/app/etc/archived_revisions/local.xml.latest | openssl dgst -sha256 -binary | xxd -p -c 256)

if [[ "${SOURCE_DIGEST}" != "${LATEST_REV_DIGEST}" ]]; then
  # display differences
  echo ""
  diff -u ${INSTALL_DIR}/app/etc/local.xml ${SHARED_DIR}/app/etc/archived_revisions/local.xml.latest
  echo -e "\nlocal.xml differences were found... archiving a revision\n"
  
  # copy file to create archived revision
  cp -a ${INSTALL_DIR}/app/etc/local.xml ${SHARED_DIR}/app/etc/archived_revisions/local.xml_${TIMESTAMP}
  echo "${SHARED_DIR}/app/etc/archived_revisions/local.xml_${TIMESTAMP}"
  
  # update latest symlink
  cd ${SHARED_DIR}/app/etc/archived_revisions
  ln -sf local.xml_${TIMESTAMP} local.xml.latest
  echo "local.xml.latest -> local.xml_${TIMESTAMP}"
fi