controller: move controllers out of commands into separate package

Signed-off-by: Justin Chadwell <me@jedevc.com>

controller/controller.go

@@ -0,0 +1,27 @@
+package controller
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/docker/buildx/controller/control"
+	"github.com/docker/buildx/controller/local"
+	"github.com/docker/buildx/controller/remote"
+	"github.com/docker/cli/cli/command"
+	"github.com/sirupsen/logrus"
+)
+
+func NewController(ctx context.Context, opts control.ControlOptions, dockerCli command.Cli) (c control.BuildxController, err error) {
+	if !opts.Detach {
+		logrus.Infof("launching local buildx controller")
+		c = local.NewLocalBuildxController(ctx, dockerCli)
+		return c, nil
+	}
+
+	logrus.Infof("connecting to buildx server")
+	c, err = remote.NewRemoteBuildxController(ctx, dockerCli, opts)
+	if err != nil {
+		return nil, fmt.Errorf("failed to use buildx server; use --detach=false: %w", err)
+	}
+	return c, nil
+}