add flag to provide docker test image as tarball

some teams would like to use `kiln test` from concourse. That concourse
could be shared, like runway // tpe concourse instances. These, even
using authentication, are getting rate limited against dockerhub.

Effectively to run kiln test, we'd first need to preload the images
required to build the test image ( every FROM arg used in the Dockerfile)
avoid the pull ibeing executed implicitly when docker build is run by `kiln test`

To avoid having to actually build an image ( which would either require
to preload the images for the Dockerfile or being able to pull from dockerhub)
we could use this flag to run `docker load -i $IMAGE_PATH` instead of building.

this way, the test image can be `acquired` via docker proxy registries..

internal/commands/test_tile.go

@@ -16,13 +16,13 @@ type TileTestFunction func(ctx context.Context, w io.Writer, configuration test.
 
 type TileTest struct {
 	Options struct {
-		TilePath   string `             long:"tile-path"                default:"."                             description:"Path to the Tile directory (e.g., ~/workspace/tas/ist)."`
-		Verbose    bool   `short:"v"    long:"verbose"                  default:"true"                          description:"Print info lines. This doesn't affect Ginkgo output."`
-		Silent     bool   `short:"s"    long:"silent"                   default:"false"                         description:"Hide info lines. This doesn't affect Ginkgo output."`
-		Manifest   bool   `             long:"manifest"                 default:"false"                         description:"Focus the Manifest tests."`
-		Migrations bool   `             long:"migrations"               default:"false"                         description:"Focus the Migration tests."`
-		Stability  bool   `             long:"stability"                default:"false"                         description:"Focus the Stability tests."`
-
+		TilePath        string   `             long:"tile-path"                default:"."                             description:"Path to the Tile directory (e.g., ~/workspace/tas/ist)."`
+		Verbose         bool     `short:"v"    long:"verbose"                  default:"true"                          description:"Print info lines. This doesn't affect Ginkgo output."`
+		Silent          bool     `short:"s"    long:"silent"                   default:"false"                         description:"Hide info lines. This doesn't affect Ginkgo output."`
+		Manifest        bool     `             long:"manifest"                 default:"false"                         description:"Focus the Manifest tests."`
+		Migrations      bool     `             long:"migrations"               default:"false"                         description:"Focus the Migration tests."`
+		Stability       bool     `             long:"stability"                default:"false"                         description:"Focus the Stability tests."`
+		ImagePath       string   "             long:\"image-path\"               "
 		EnvironmentVars []string `short:"e"    long:"environment-variable"                                             description:"Pass environment variable to the test suites. For example --stability -e 'PRODUCT=srt'."`
 		GingkoFlags     string   `             long:"ginkgo-flags"             default:"-r -p -slowSpecThreshold 15"   description:"Flags to pass to the Ginkgo Manifest and Stability test suites."`
 	}
@@ -70,6 +70,7 @@ func (cmd TileTest) configuration() (test.Configuration, error) {
 		RunManifest:   cmd.Options.Manifest,
 		RunMetadata:   cmd.Options.Stability,
 		RunMigrations: cmd.Options.Migrations,
+		ImagePath:     cmd.Options.ImagePath,
 
 		GinkgoFlags: cmd.Options.GingkoFlags,
 		Environment: cmd.Options.EnvironmentVars,

internal/commands/test_tile_test.go

@@ -208,6 +208,27 @@ var _ = Describe("kiln test", func() {
 		})
 	})
 
+	When("when the a test image is provided via --image-path", func() {
+		It("it sets the path to be loaded in the configuration", func() {
+			args := []string{"--image-path", "/tmp/test.file"}
+
+			fakeTestFunc := fakes.TestTileFunction{}
+			fakeTestFunc.Returns(nil)
+
+			err := commands.NewTileTestWithCollaborators(&output, fakeTestFunc.Spy).Execute(args)
+			Expect(err).NotTo(HaveOccurred())
+
+			Expect(fakeTestFunc.CallCount()).To(Equal(1))
+
+			ctx, w, configuration := fakeTestFunc.ArgsForCall(0)
+			Expect(ctx).NotTo(BeNil())
+			Expect(w).NotTo(BeNil())
+			Expect(configuration.ImagePath).To(Equal("/tmp/test.file"))
+			Expect(configuration.RunManifest).To(BeFalse())
+			Expect(configuration.RunMetadata).To(BeFalse())
+			Expect(configuration.RunMigrations).To(BeFalse())
+		})
+	})
 	When("when the stability test is enabled", func() {
 		It("it sets the metadata configuration flag", func() {
 			args := []string{"--stability"}

internal/test/container.go

@@ -89,6 +89,7 @@ type Configuration struct {
 	RunMigrations,
 	RunManifest,
 	RunMetadata bool
+	ImagePath string
 
 	GinkgoFlags string
 	Environment []string