fix: use buildx builder if provided

_docs/data/data.yaml

@@ -1,5 +1,10 @@
 ---
 properties:
+  builder_name:
+    description: Buildx builder to use.
+    type: string
+    required: false
+
   dry_run:
     description: Disable docker push.
     type: bool

cmd/drone-docker-buildx/config.go

@@ -9,6 +9,13 @@ import (
 // settingsFlags has the cli.Flags for the plugin.Settings.
 func settingsFlags(settings *plugin.Settings, category string) []cli.Flag {
 	return []cli.Flag{
+		&cli.StringFlag{
+			Name:        "builder-name",
+			EnvVars:     []string{"PLUGIN_BUILDER_NAME"},
+			Usage:       "the buildx builder to use",
+			Destination: &settings.Build.BuilderName,
+			Category:    category,
+		},
 		&cli.BoolFlag{
 			Name:        "dry-run",
 			EnvVars:     []string{"PLUGIN_DRY_RUN"},

plugin/docker.go

@@ -75,6 +75,9 @@ func commandBuild(build Build, dryrun bool) *exec.Cmd {
 	}
 
 	args = append(args, build.Context)
+	if build.BuilderName != "" {
+		args = append(args, "--builder-name", build.BuilderName)
+	}
 	if !dryrun && build.Output == "" && len(build.Tags.Value()) > 0 {
 		args = append(args, "--push")
 	}

plugin/impl.go

@@ -63,6 +63,7 @@ type Build struct {
 	Output       string          // Docker build output folder
 	NamedContext cli.StringSlice // Docker build named context
 	Labels       cli.StringSlice // Docker build labels
+	BuilderName  string          // Docker buildx builder
 }
 
 // Settings for the Plugin.