stickshift.js
function extendSelection(doc, head, other, options) {
    setSelection(doc, new Selection([extendRange(doc, doc.sel.primary(), head, other)], 0), options);
  }
function extendSelection(doc, head, other, options) {
    setSelection(doc, new Selection([extendRange(doc, doc.sel.primary(), head, other)], 0), options);
  }
function extendSelection ( doc , head , other , options ) { setSelection ( doc , new Selection ( [ extendRange ( doc , doc . sel . primary ( ) , head , other ) ] , 0 ) , options ) ; }
Extend the primary selection range, discard the rest.
Extend the primary selection range discard the rest .