Add identical check

lib/boxing/generator.rb

@@ -18,6 +18,8 @@ def initialize(destination, content)
     #
     # @since 0.11.0
     def execute
+      return if identical?
+
       FileUtils.mkdir_p(File.dirname(@destination))
       File.write(@destination, render)
     end
@@ -34,5 +36,23 @@ def render
                     @content
                   end
     end
+
+    # Check if file exists
+    #
+    # @return [TrueClass|FalseClass]
+    #
+    # @since 0.11.0
+    def exist?
+      @destination.exist?
+    end
+
+    # Check if file identical
+    #
+    # @return [TrueClass|FalseClass]
+    #
+    # @since 0.11.0
+    def identical?
+      exist? && File.binread(@destination) == String.new(render).force_encoding('ASCII-8BIT')
+    end
   end
 end

spec/boxing/generator_spec.rb

@@ -19,4 +19,11 @@
   it 'writes the template to the file' do
     expect(File.read(File.join(tmpdir, 'Dockerfile'))).to eq 'test'
   end
+
+  context 'when file identically exists' do
+    before { generator.execute }
+
+    it { is_expected.to be_exist }
+    it { is_expected.to be_identical }
+  end
 end