copies: properly copies parent dictionary before updating it
This enforces the copy on write logic. Otherwise independant unrelated branches
could affected each other.
More testing of these case are coming, but I need that code landed to unlock
other performance work in parallel.
Differential Revision: https://phab.mercurial-scm.org/D9419
{
// 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)
}