simplemerge: use 3-way markers if mode=='merge3', ignoring number of labels
Before this patch, we use a combination of `mode` and `labels` to
decide which marker style to use. That's mostly my own fault because I
was the one who added the `mergediff` as a "mode" instead of adding a
separate argument for marker style. Still, let's make these arguments
more orthogonal by ignoring the number of labels when deciding which
marker style to use.
This refactoring makes it a little clearer in the simplemerge
*extension* that passing more than 2 `--label` arguments changes the
marker style.
Differential Revision: https://phab.mercurial-scm.org/D11972
{
// 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)
}