Installing WordPress submodule

Updating a WordPress blog with all its plug-ins may be very time-consuming, especially for those who maintain several blogs. Fortunately, there is a solution to reduce maintenance time. Using Git, you will be able to update your blogs just by checking out the new tag of your WordPress submodule.

First, create a project and initialize it:

mkdir blog
git init

Now, retrieve WordPress Git repository and add it as a submodule:

git submodule add https://github.com/WordPress/WordPress wordpress

For stability reasons, it is recommended to stabilize submodules to tags or branches considered as stable. So, let’s apply this best practice by fixing WordPress version to current one (3.4.2 when I wrote this post).

cd wordpress
git fetch -a
git tag
git checkout 3.4.2

These lines simply go to the submodule repository to retrieve all remote tags (with git fetch command). Then, we display all available tags and fix the version to 3.4.2 with checkout command.

Commit your work before configuring WordPress to use this Git architecture:

git commit -m "Install WordPress 3.4.2 as a submodule"

Configuring WordPress to use Git submodule

Duplicate all files you will change to be able to commit them into your own repository (and not into WordPress core):

cp wordpress/index.php index.php
cp wordpress/wp-config-sample.php wp-config.php
cp -Rf wordpress/wp-content .

rm -Rf wp-content/plugins/hello.php wp-content/themes/twentyten

The three first lines simply copy files we will modify. The last one cleans our repository, removing useless hello plug-in and default twentyten theme.

Commit these changes:

git commit -am "Duplicate all non-core WordPress files"

Now, we have to tell WordPress to use our new structure: the submodule for all the core files, and the root wp-content folder for all other stuff.

First, let’s edit the index.php file to indicate WordPress where the bootstrap file is. Replace line 17 by:

require('wordpress/wp-blog-header.php');

Then, edit your wp-config.php configuration file according to your own situation. Just follow the comments.

Yet, we will define in this file some constants to take the new structure into account. Add the following lines into this same file, before the require_once(ABSPATH . 'wp-settings.php'); line (thanks to Marco Neumann for this precision):

define('WP_HOME',    'http://'.$_SERVER['SERVER_NAME']);
define('WP_SITEURL', WP_HOME.'/wordpress');

define('WP_CONTENT_DIR', $_SERVER['DOCUMENT_ROOT'].'/wp-content');
define('WP_CONTENT_URL', WP_HOME.'/wp-content');

Your blog should now be accessible. Do not forget to commit your changes:

git commit -am "Configure WordPress to be used as a Git submodule"

If you want to connect to the administration panel, simply go to wordpress/wp-admin URL. Or, if you rather like to use standard access, simply create a symbolic link:

ln -s wordpress/wp-admin .

How to update WordPress as a submodule?

Here is the process to update easily your WordPress installation:

cd wordpress
git fetch -a
git tag
git checkout 3.4.3
cd ..
git commit -am "Switch WordPress to 3.4.3 version"

It is the same we have seen before. It consists to fetch all recently created tags and branches, and to change current version.

It is equivalent for all the plug-ins and/or themes… at least, if they have a Git repository, which is not often the case. Pretty sad for open-source, isn’t it?