monitor: Move commands to a separated package

This commit moves monitor commands to `monior/commands` package.
Commands still need access to the `monitor` object and buildx controller so this
commit enables this via `Monitor` interface stored in `monitor/types`.

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>

monitor/commands/reload.go

@@ -0,0 +1,76 @@
+package commands
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	controllererrors "github.com/docker/buildx/controller/errdefs"
+	controllerapi "github.com/docker/buildx/controller/pb"
+	"github.com/docker/buildx/monitor/types"
+	"github.com/docker/buildx/util/progress"
+	"github.com/pkg/errors"
+)
+
+type ReloadCmd struct {
+	m types.Monitor
+
+	stdout   io.WriteCloser
+	progress *progress.Printer
+
+	options      *controllerapi.BuildOptions
+	invokeConfig controllerapi.InvokeConfig
+}
+
+func NewReloadCmd(m types.Monitor, stdout io.WriteCloser, progress *progress.Printer, options *controllerapi.BuildOptions, invokeConfig controllerapi.InvokeConfig) types.Command {
+	return &ReloadCmd{m, stdout, progress, options, invokeConfig}
+}
+
+func (cm *ReloadCmd) Info() types.CommandInfo {
+	return types.CommandInfo{HelpMessage: "reloads the context and build it"}
+}
+
+func (cm *ReloadCmd) Exec(ctx context.Context, args []string) error {
+	var bo *controllerapi.BuildOptions
+	if cm.m.AttachedSessionID() != "" {
+		// Rebuilding an existing session; Restore the build option used for building this session.
+		res, err := cm.m.Inspect(ctx)
+		if err != nil {
+			fmt.Printf("failed to inspect the current build session: %v\n", err)
+		} else {
+			bo = res.Options
+		}
+	} else {
+		bo = cm.options
+	}
+	if bo == nil {
+		return errors.Errorf("no build option is provided")
+	}
+	if cm.m.AttachedSessionID() != "" {
+		if err := cm.m.Disconnect(ctx); err != nil {
+			fmt.Println("disconnect error", err)
+		}
+	}
+	var resultUpdated bool
+	cm.progress.Unpause()
+	ref, _, err := cm.m.Build(ctx, *bo, nil, cm.progress) // TODO: support stdin, hold build ref
+	cm.progress.Pause()
+	if err != nil {
+		var be *controllererrors.BuildError
+		if errors.As(err, &be) {
+			ref = be.Ref
+			resultUpdated = true
+		} else {
+			fmt.Printf("failed to reload: %v\n", err)
+		}
+	} else {
+		resultUpdated = true
+	}
+	cm.m.AttachSession(ref)
+	if resultUpdated {
+		// rollback the running container with the new result
+		id := cm.m.Rollback(ctx, cm.invokeConfig)
+		fmt.Fprintf(cm.stdout, "Interactive container was restarted with process %q. Press Ctrl-a-c to switch to the new container\n", id)
+	}
+	return nil
+}