graph: add parent img refcount for faster rmi

also fix a typo in pkg/truncindex package comment

Signed-off-by: Antonio Murdaca <runcom@redhat.com>

integration-cli/docker_cli_images_test.go

@@ -51,7 +51,6 @@ func (s *DockerSuite) TestImagesEnsureImageWithBadTagIsNotListed(c *check.C) {
 	if strings.Contains(out, "busybox") {
 		c.Fatal("images should not have listed busybox")
 	}
-
 }
 
 func (s *DockerSuite) TestImagesOrderedByCreationDate(c *check.C) {
@@ -204,3 +203,42 @@ func (s *DockerSuite) TestImagesWithIncorrectFilter(c *check.C) {
 	c.Assert(err, check.NotNil)
 	c.Assert(out, checker.Contains, "Invalid filter")
 }
+
+func (s *DockerSuite) TestImagesEnsureOnlyHeadsImagesShown(c *check.C) {
+	testRequires(c, DaemonIsLinux)
+
+	dockerfile := `
+        FROM scratch
+        MAINTAINER docker
+        ENV foo bar`
+
+	head, out, err := buildImageWithOut("scratch-image", dockerfile, false)
+	c.Assert(err, check.IsNil)
+
+	split := strings.Split(out, "\n")
+	intermediate := strings.TrimSpace(split[5][7:])
+
+	out, _ = dockerCmd(c, "images")
+	if strings.Contains(out, intermediate) {
+		c.Fatalf("images shouldn't show non-heads images, got %s in %s", intermediate, out)
+	}
+	if !strings.Contains(out, head[:12]) {
+		c.Fatalf("images should contain final built images, want %s in out, got %s", head[:12], out)
+	}
+}
+
+func (s *DockerSuite) TestImagesEnsureImagesFromScratchShown(c *check.C) {
+	testRequires(c, DaemonIsLinux)
+
+	dockerfile := `
+        FROM scratch
+        MAINTAINER docker`
+
+	id, _, err := buildImageWithOut("scratch-image", dockerfile, false)
+	c.Assert(err, check.IsNil)
+
+	out, _ := dockerCmd(c, "images")
+	if !strings.Contains(out, id[:12]) {
+		c.Fatalf("images should contain images built from scratch (e.g. %s), got %s", id[:12], out)
+	}
+}

integration-cli/docker_cli_rmi_test.go

@@ -354,3 +354,15 @@ RUN echo 2 #layer2
 		c.Fatalf("%q should be allowed to untag with the -f flag", newTag)
 	}
 }
+
+func (*DockerSuite) TestRmiParentImageFail(c *check.C) {
+	testRequires(c, DaemonIsLinux)
+
+	parent, err := inspectField("busybox", "Parent")
+	c.Assert(err, check.IsNil)
+	out, _, err := dockerCmdWithError("rmi", parent)
+	c.Assert(err, check.NotNil)
+	if !strings.Contains(out, "image has dependent child images") {
+		c.Fatalf("rmi should have failed because it's a parent image, got %s", out)
+	}
+}