Ability to overwrite an existing manifest

Sometimes amend is not enough, especially when `--purge` was
not used during `manifest push` command. And since we don't have a
`manifest delete` either to clean up. So just adding an `--overwrite`
seems like a good thought.

Change-Id: I473952ae434f421b6345c28db5cfdfcc49614710
Signed-off-by: Davanum Srinivas <davanum@gmail.com>

Author: dims

cli/command/manifest/create_list.go

@@ -13,8 +13,9 @@ import (
 )
 
 type createOpts struct {
-	amend    bool
-	insecure bool
+	amend     bool
+	overwrite bool
+	insecure  bool
 }
 
 func newCreateListCommand(dockerCli command.Cli) *cobra.Command {
@@ -32,6 +33,7 @@ func newCreateListCommand(dockerCli command.Cli) *cobra.Command {
 	flags := cmd.Flags()
 	flags.BoolVar(&opts.insecure, "insecure", false, "Allow communication with an insecure registry")
 	flags.BoolVarP(&opts.amend, "amend", "a", false, "Amend an existing manifest list")
+	flags.BoolVarP(&opts.amend, "overwrite", "o", false, "Remove an existing manifest list if any and start fresh")
 	return cmd
 }
 
@@ -55,7 +57,11 @@ func createManifestList(dockerCli command.Cli, args []string, opts createOpts) e
 	case err != nil:
 		return err
 	case !opts.amend:
-		return errors.Errorf("refusing to amend an existing manifest list with no --amend flag")
+		if opts.overwrite {
+			manifestStore.Remove(targetRef)
+		} else {
+			return errors.Errorf("refusing to amend an existing manifest list with no --amend flag")
+		}
 	}
 
 	ctx := context.Background()

cli/command/manifest/create_test.go

@@ -92,6 +92,26 @@ func TestManifestCreateRefuseAmend(t *testing.T) {
 	assert.Error(t, err, "refusing to amend an existing manifest list with no --amend flag")
 }
 
+// Successfully overwrite a saved manifest
+func TestManifestCreateOverwrite(t *testing.T) {
+	store, cleanup := newTempManifestStore(t)
+	defer cleanup()
+
+	cli := test.NewFakeCli(nil)
+	cli.SetManifestStore(store)
+	namedRef := ref(t, "alpine:3.0")
+	imageManifest := fullImageManifest(t, namedRef)
+	err := store.Save(ref(t, "list:v1"), namedRef, imageManifest)
+	assert.NilError(t, err)
+
+	cmd := newCreateListCommand(cli)
+	cmd.SetArgs([]string{"example.com/list:v1", "example.com/alpine:3.0"})
+	cmd.Flags().Set("overwrite", "true")
+	cmd.SetOutput(ioutil.Discard)
+	err = cmd.Execute()
+	assert.NilError(t, err)
+}
+
 // attempt to make a manifest list without valid images
 func TestManifestCreateNoManifest(t *testing.T) {
 	store, cleanup := newTempManifestStore(t)