upgrade: move optimisation to something more declarative
This is not great yet, but still better than the previous state. This get use
one step closer to having all the possible "actions" clearly declared and moved
in a dedicated module.
Differential Revision: https://phab.mercurial-scm.org/D9475
{
// Enforcing
"eqeqeq" : true, // true: Require triple equals (===) for comparison
"forin" : true, // true: Require filtering for..in loops with obj.hasOwnProperty()
"freeze" : true, // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
"nonbsp" : true, // true: Prohibit "non-breaking whitespace" characters.
"undef" : true, // true: Require all non-global variables to be declared (prevents global leaks)
// Environments
"browser" : true // Web Browser (window, document, etc)
}