Fix for diff text formatter equality testing

Ensures that changes in the `line_range` attr are detected.

lib/gitlab/diff/formatters/text_formatter.rb

@@ -45,7 +45,8 @@ module Gitlab
         def ==(other)
           other.is_a?(self.class) &&
             new_line == other.new_line &&
-            old_line == other.old_line
+            old_line == other.old_line &&
+            line_range == other.line_range
         end
       end
     end

spec/lib/gitlab/diff/formatters/text_formatter_spec.rb

@@ -26,6 +26,7 @@ describe Gitlab::Diff::Formatters::TextFormatter do
 
   # Specific text formatter examples
   let!(:formatter) { described_class.new(attrs) }
+  let(:attrs) { base }
 
   describe '#line_age' do
     subject { formatter.line_age }
@@ -42,4 +43,21 @@ describe Gitlab::Diff::Formatters::TextFormatter do
       it { is_expected.to eq('old') }
     end
   end
+
+  describe "#==" do
+    it "is false when the line_range changes" do
+      formatter_1 = described_class.new(base.merge(line_range: { start_line_code: "foo", end_line_code: "bar" }))
+      formatter_2 = described_class.new(base.merge(line_range: { start_line_code: "foo", end_line_code: "baz" }))
+
+      expect(formatter_1).not_to eq(formatter_2)
+    end
+
+    it "is true when the line_range doesn't change" do
+      attrs = base.merge({ line_range: { start_line_code: "foo", end_line_code: "baz" } })
+      formatter_1 = described_class.new(attrs)
+      formatter_2 = described_class.new(attrs)
+
+      expect(formatter_1).to eq(formatter_2)
+    end
+  end
 end