use value instead url in file's link_to body

[buncis]

use filename/value instead full url in file's link_to body

[mshibuya]

Could you write a spec for this?

[buncis]

@mshibuya I want to write the spec, but I don't know how since it have no spec before, can you guide me how to write the spec? thank you

  describe '#pretty_value' do
    it 'use value instead url for link_to body' do
      expect().to eq value
    end
  end

[mshibuya]

Cherry-picked as e3770ba.