Extension:MediaWikiFarm/Internals

Composer-installed extensions
2 possible strategies:
 * 1) Bold: a script (mwcomposer.php) iterates overs Composer-installed extensions and skins (type: mediawiki-extension or mediawiki-skin), creates as much /vendor/composer directories as there are combinations (= 2^n = \sum_{k=0}^n C(n,k), where n = #extensions), each one with a key (e.g. a hash of its content), then replaces the /vendor/autoload.php by a customised file; this one get the Composer key from MediaWiki (for now when used in multiversion mode, since configuration can be loaded before in this mode) and require_once the right composer subdirectory.
 * 2) Conservative: similar to the previous scenario, but creates as much MediaWiki directories as there are combinaisons (2^n)

Benefits/drawbacks:
 * 1) Bold:
 * 2) *  less disk space used, cleaner (not many MW installations)
 * 3) *  bold (more issues expected), the customised binary Composer must be used instead
 * 4) Conservative:
 * 5) *  fully compatible with MediaWiki and Composer, even old versions
 * 6) *  more disk space used, less practical to manage MediaWiki