grep: give different labels to + and - symbols
I find it more useful to give different colours to plus and minus, but
it's difficult to do so if the default output uses the same label for
both. The following augments the names of columns with some extra
labels, akin to the diff.inserted and diff.deleted labels for the diff
command.
This is done by adding an extra label field to the columns tuples.
{
// 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)
}