Verify cache support works

lib/docker/util.rb

@@ -138,15 +138,40 @@ def create_relative_dir_tar(directory, output)
         next unless stat.file?
 
         unprefixed_file_name = prefixed_file_name[directory.length..-1]
-        tar.add_file_simple(
-          unprefixed_file_name, stat.mode, stat.size
+        add_file_to_tar(
+          tar, unprefixed_file_name, stat.mode, stat.size, stat.mtime
         ) do |tar_file|
           IO.copy_stream(File.open(prefixed_file_name, 'rb'), tar_file)
         end
       end
     end
   end
 
+  def add_file_to_tar(tar, name, mode, size, mtime)
+    tar.check_closed
+
+    io = tar.instance_variable_get(:@io)
+
+    name, prefix = tar.split_name(name)
+
+    header = Gem::Package::TarHeader.new(:name => name, :mode => mode,
+                                         :size => size, :prefix => prefix,
+                                         :mtime => mtime).to_s
+
+    io.write header
+    os = Gem::Package::TarWriter::BoundedStream.new io, size
+
+    yield os if block_given?
+
+    min_padding = size - os.written
+    io.write("\0" * min_padding)
+
+    remainder = (512 - (size % 512)) % 512
+    io.write("\0" * remainder)
+
+    tar
+  end
+
   def create_temp_file
     tempfile_name = Dir::Tmpname.create('out') {}
     File.open(tempfile_name, 'wb+')

spec/docker/image_spec.rb

@@ -564,30 +564,37 @@
         Docker::Container.create('Image' => image.id,
                                  'Cmd' => %w[cat /Dockerfile])
       end
-      let!(:output) {
-        container.tap(&:start).streaming_logs(stdout: true)
-      }
+      let(:output) { container.streaming_logs(stdout: true) }
+
       after(:each) do
-        container.tap(&:wait).remove
         image.remove(:noprune => true)
       end
 
       context 'with no query parameters' do
         it 'builds the image', :vcr do
-          container.wait
+          container.tap(&:wait).start
           expect(output).to eq(docker_file.read)
         end
+
+        after do
+          container.remove
+        end
       end
 
       context 'with specifying a repo in the query parameters' do
         let(:opts) { { "t" => "#{ENV['DOCKER_API_USER']}/debian:from_dir" } }
         it 'builds the image and tags it', :vcr do
+          container.tap(&:wait).start
           expect(output).to eq(docker_file.read)
           image.refresh!
           expect(image.info["RepoTags"]).to eq(
             ["#{ENV['DOCKER_API_USER']}/debian:from_dir"]
           )
         end
+
+        after do
+          container.remove
+        end
       end
 
       context 'with a block capturing build output' do
@@ -598,6 +605,21 @@
           image # Create the image variable, which is lazy-loaded by Rspec
           expect(build_output).to match(/Step 0 : FROM debian:wheezy/)
         end
+
+        context 'uses a cached version the second time' do
+          let(:build_output_two) { "" }
+          let(:block_two) { Proc.new { |chunk| build_output_two << chunk } }
+          let(:image_two) { subject.build_from_dir(dir, opts, &block_two) }
+
+          it 'calls the block and passes build output', :vcr do
+            image # Create the image variable, which is lazy-loaded by Rspec
+            expect(build_output).to match(/Step 0 : FROM debian:wheezy/)
+            expect(build_output).to_not match(/Using cache/)
+
+            image_two # Create the image_two variable, which is lazy-loaded by Rspec
+            expect(build_output_two).to match(/Using cache/)
+          end
+        end
       end
 
       context 'with credentials passed' do

spec/support/vcr.rb

@@ -4,7 +4,7 @@
 
 VCR.configure do |c|
   c.allow_http_connections_when_no_cassette = false
-  c.filter_sensitive_data('<DOCKER_HOST>') { Docker.url.sub(/tcp\:/, 'https:') }
+  c.filter_sensitive_data('<DOCKER_HOST>') { Docker.url }
   c.filter_sensitive_data('<USERNAME>') { ENV['DOCKER_API_USER'] }
   c.filter_sensitive_data('<PASSWORD>') { ENV['DOCKER_API_PASS'] }
   c.filter_sensitive_data('<EMAIL>') { ENV['DOCKER_API_EMAIL'] }