anchor.diff:              gradientFill&attributes()
       borders(count=borders.length)
         each border, r in borders
  -        if Object.keys(border).length === 1
  +        if !border || Object.keys(border).length === 1
             border/
           else
             border
  
positive.code:       xf(borderId="0" fillId="0" fontId="0" numFmtId="0")/
      cellXfs(count=cellStyles.length)
        each style, t in cellStyles
          - var fillId = ('fill' in style && style.fill) || 0
          - var borderId = ('border' in style && style.border) || 0
          - var numberFormat = ('numberFormat' in style && (style.numberFormat + 200)) || 0
          if Object.keys(style).length === 1
            xf/
          else
            xf(
  
negative.code: extends ./xml.jade
  include ./mixins/attrTags.jade
  
  mixin valTag(tag, val)
    - var tagMap = {size: 'sz'}
  