narrow: add support for merging add and remove outside of the tracked set
This extend f1eb77dceb36 to test and support the remaining action. Or, at least,
the simple incarnation of them.
Differential Revision: https://phab.mercurial-scm.org/D12181
{
// 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)
}