It's a command-line tool that downloads required libraries into the `vendor` folder and makes any namespaced class in `src` available through the whole application through `boot.php`.
+If you want to have git automatically update the dependencies with composer, you can use the `post-merge` [git-hook](https://git-scm.com/book/en/v2/Customizing-Git-Git-Hooks) with a script similar to this one:
+
+ #/usr/bin/env bash
+ # MIT © Sindre Sorhus - sindresorhus.com
+ # forked by Gianluca Guarini
+ # phponly by Ivo Bathke ;)
+ # modified for Friendica by Tobias Diekershoff
+ changed_files="$(git diff-tree -r --name-only --no-commit-id ORIG_HEAD HEAD)"
+ check_run() {
+ echo "$changed_files" | grep --quiet "$1" && eval "$2"
+ }
+ # `composer install` if the `composer.lock` file gets changed
+ # to update all the php dependencies
+ check_run composer.lock "util/composer.phar install --no-dev"
+
+just place it into `.git/hooks/post-merge` and make it executeable.
+
* [Class autoloading](help/autoloader)
* [Using Composer](help/Composer)
* [How To Move Classes to `src`](help/Developer-How-To-Move-Classes-to-src)