Also convert cacheto to workaround

cmd/docker-buildx/config.go

@@ -196,11 +196,11 @@ func settingsFlags(settings *plugin.Settings) []cli.Flag {
 			Usage:   "images to consider as cache sources",
 			Value:   &drone.StringSliceFlag{},
 		},
-		&cli.StringSliceFlag{
+		&cli.GenericFlag{
 			Name:        "cache-to",
 			EnvVars:     []string{"PLUGIN_CACHE_TO"},
 			Usage:       "cache destination for the build cache",
-			Destination: &settings.Build.CacheTo,
+			Destination: &drone.StringSliceFlag{},
 		},
 		&cli.BoolFlag{
 			Name:        "pull-image",

cmd/docker-buildx/main.go

@@ -47,9 +47,14 @@ func run(settings *plugin.Settings) cli.ActionFunc {
 		if !ok {
 			return fmt.Errorf("failed to read cache-from input")
 		}
-
 		settings.Build.CacheFrom = cacheFrom.Get()
 
+		cacheTo, ok := ctx.Generic("cache-to").(*drone.StringSliceFlag)
+		if !ok {
+			return fmt.Errorf("failed to read cache-to input")
+		}
+		settings.Build.CacheTo = cacheTo.Get()
+
 		plugin := plugin.New(
 			*settings,
 			urfave.PipelineFromContext(ctx),

plugin/docker.go

@@ -81,7 +81,7 @@ func commandBuild(build Build, dryrun bool) *exec.Cmd {
 	for _, arg := range build.CacheFrom {
 		args = append(args, "--cache-from", arg)
 	}
-	for _, arg := range build.CacheTo.Value() {
+	for _, arg := range build.CacheTo {
 		args = append(args, "--cache-to", arg)
 	}
 	for _, arg := range build.ArgsEnv.Value() {

plugin/impl.go

@@ -65,7 +65,7 @@ type Build struct {
 	Output          string          // Docker build output
 	Pull            bool            // Docker build pull
 	CacheFrom       []string        // Docker build cache-from
-	CacheTo         cli.StringSlice // Docker build cache-to
+	CacheTo         []string        // Docker build cache-to
 	Compress        bool            // Docker build compress
 	Repo            cli.StringSlice // Docker build repository
 	NoCache         bool            // Docker build no-cache