Fossil

    var arw = arrowSpace < arrow.h*1.5 ? arrowSmall : arrow;
    var x = to.x + (node.w-line.w)/2;
    var y0 = from.y + node.h/2;
    var y1 = Math.ceil(to.y + node.h + arw.h/2);
    drawLine(line,color,x,y0,null,y1);
    x = to.x + (node.w-arw.w)/2;
    var n = drawBox(arw.cls,null,x,y);
    if(color) n.style.borderBottomColor = color;
  }
  function drawMergeLine(x0,y0,x1,y1){
    drawLine(mLine,null,x0,y0,x1,y1);
  }
  function drawMergeArrow(p,rail){
    var x0 = rail*railPitch + node.w/2;
    if( rail in mergeLines ){