Add docs to loadPackages

src/Composer/Repository/RepositoryInterface.php

@@ -66,6 +66,9 @@ interface RepositoryInterface extends \Countable
     /**
      * Returns list of registered packages with the supplied name
      *
+     * - The packages returned are the packages found which match the constraints, acceptable stability and stability flags provided
+     * - The namesFound returned are names which should be considered as canonically found in this repository, that should not be looked up in any further lower priority repositories
+     *
      * @param ConstraintInterface[] $packageNameMap package names pointing to constraints
      * @param array $acceptableStabilities
      * @param array $stabilityFlags