Using wp-cli to easily handle updates and other features

[w4tsn]

This pull requests contains changes for the use of wp-cli to provide some useful functionalities for wp setup through configuration management with docker-compose.

Updates to wp core and plugins are included.

Current new features (on build time):

• provide a wp_version to be included within the image; persists through ENV WP_BUILD_VERSION
• provide a wp_locale to set the language for the image source files
• provide a list of php extensions to be embedded into the image (needed for plugins)

Current new features (on runtime):

• update to the image version or provide a WORDPRESS_VERSION
• update all plugins if wordpress is installed on container startup
• provide a list of plugins through WP_PLUGINS to be installed on next container start

Possible features for the future

• direct install wordpress through env config (useful for automated setup with even plugins through config)
• provide any possible interface to the wp-cli you can think of
• add a SCRIPTS_DIR volume to map custom scripts into the image on startup

[yosifkit]

wp-cli looks like a handy to for managing WordPress installs and changes. The problem I see is that we try to stick as close to upstream and their recommendations as possible, and I don't see a recommendation from them. The closest that I can find is in the documentation for "Changing the Site URL" where they say "wp-cli is a super useful shell tool".

[mwpastore]

Even just having wp-cli available in the image would be a killer feature. Also, this was in the news last week: https://wptavern.com/wp-cli-gets-official-wordpress-org-support