Add the --target flag as a parameter to the docker builder.

examples/annotated-skaffold.yaml

@@ -53,6 +53,8 @@ build:
       cacheFrom:
       - image1
       - image2
+      # Dockerfile target name to build.
+      # target: stageName
 
     # bazel requires bazel CLI to be installed and the artifacts sources to
     # contain Bazel configuration files.

pkg/skaffold/build/local/docker.go

@@ -40,9 +40,6 @@ func (b *Builder) buildDocker(ctx context.Context, out io.Writer, workspace stri
 
 		args := []string{"build", workspace, "--file", dockerfilePath, "-t", initialTag}
 		args = append(args, docker.GetBuildArgs(a)...)
-		for _, from := range a.CacheFrom {
-			args = append(args, "--cache-from", from)
-		}
 
 		cmd := exec.Command("docker", args...)
 		if b.cfg.UseBuildkit {

pkg/skaffold/docker/image.go

@@ -66,6 +66,7 @@ func BuildArtifact(ctx context.Context, out io.Writer, cli APIClient, workspace
 		BuildArgs:   a.BuildArgs,
 		CacheFrom:   a.CacheFrom,
 		AuthConfigs: authConfigs,
+		Target:      a.Target,
 	})
 	if err != nil {
 		return errors.Wrap(err, "docker build")
@@ -194,5 +195,13 @@ func GetBuildArgs(a *v1alpha2.DockerArtifact) []string {
 		}
 	}
 
+	for _, from := range a.CacheFrom {
+		args = append(args, "--cache-from", from)
+	}
+
+	if a.Target != "" {
+		args = append(args, "--target", a.Target)
+	}
+
 	return args
 }

pkg/skaffold/docker/image_test.go

@@ -171,18 +171,56 @@ func TestDigest(t *testing.T) {
 }
 
 func TestGetBuildArgs(t *testing.T) {
-	artifact := &v1alpha2.DockerArtifact{
-		BuildArgs: map[string]*string{
-			"key1": util.StringPtr("value1"),
-			"key2": nil,
+	type args struct {
+		a *v1alpha2.DockerArtifact
+	}
+	tests := []struct {
+		description string
+		artifact    *v1alpha2.DockerArtifact
+		want        []string
+	}{
+		{
+			description: "build args",
+			artifact: &v1alpha2.DockerArtifact{
+				BuildArgs: map[string]*string{
+					"key1": util.StringPtr("value1"),
+					"key2": nil,
+				},
+			},
+			want: []string{"--build-arg", "key1=value1", "--build-arg", "key2"},
+		},
+		{
+			description: "cache from",
+			artifact: &v1alpha2.DockerArtifact{
+				CacheFrom: []string{"gcr.io/foo/bar", "baz:latest"},
+			},
+			want: []string{"--cache-from", "gcr.io/foo/bar", "--cache-from", "baz:latest"},
+		},
+		{
+			description: "target",
+			artifact: &v1alpha2.DockerArtifact{
+				Target: "stage1",
+			},
+			want: []string{"--target", "stage1"},
+		},
+		{
+			description: "all",
+			artifact: &v1alpha2.DockerArtifact{
+				BuildArgs: map[string]*string{
+					"key1": util.StringPtr("value1"),
+				},
+				CacheFrom: []string{"foo"},
+				Target:    "stage1",
+			},
+			want: []string{"--build-arg", "key1=value1", "--cache-from", "foo", "--target", "stage1"},
 		},
 	}
-
-	arg := GetBuildArgs(artifact)
-	expected := []string{"--build-arg", "key1=value1", "--build-arg", "key2"}
-
-	if diff := cmp.Diff(arg, expected); diff != "" {
-		t.Errorf("%T differ (-got, +want): %s", expected, diff)
-		return
+	for _, tt := range tests {
+		t.Run(tt.description, func(t *testing.T) {
+			result := GetBuildArgs(tt.artifact)
+			if diff := cmp.Diff(result, tt.want); diff != "" {
+				t.Errorf("%T differ (-got, +want): %s", tt.want, diff)
+			}
+		})
 	}
 }

pkg/skaffold/schema/v1alpha2/config.go

@@ -210,6 +210,7 @@ type DockerArtifact struct {
 	DockerfilePath string             `yaml:"dockerfilePath,omitempty"`
 	BuildArgs      map[string]*string `yaml:"buildArgs,omitempty"`
 	CacheFrom      []string           `yaml:"cacheFrom,omitempty"`
+	Target         string             `yaml:"target,omitempty"`
 }
 
 type BazelArtifact struct {