keep a copy of moved dropin/mu-plugins files, so we can prepare the patches

composer.json

@@ -20,6 +20,9 @@
             "url": "git@git.autistici.org:lucha/r2db.git"
         }
     ],
+    "config": {        
+        "dropin-installer": "copy"
+    },
     "require": {
         "php": ">=7.1",
         "composer/installers": "^1.8",