implement new 'zrepl status'

Primary goals:

- Scrollable output ( fixes #245 )
- Sending job signals from status view
- Filtering of output by filesystem

Implementation:

- original TUI framework: github.com/rivo/tview
- but: tview is quasi-unmaintained, didn't support some features
- => use fork https://gitlab.com/tslocum/cview
- however, don't buy into either too much to avoid lock-in

- instead: **port over the existing status UI drawing code
  and adjust it to produce strings instead of directly
  drawing into the termbox buffer**

Co-authored-by: Calistoc <calistoc@protonmail.com>
Co-authored-by: InsanePrawn <insane.prawny@gmail.com>

fixes #245
fixes #220

client/status/status.go

@@ -0,0 +1,94 @@
+package status
+
+import (
+	"context"
+	"os"
+	"time"
+
+	"github.com/mattn/go-isatty"
+	"github.com/pkg/errors"
+	"github.com/spf13/pflag"
+
+	"github.com/zrepl/zrepl/cli"
+	"github.com/zrepl/zrepl/client/status/client"
+	"github.com/zrepl/zrepl/config"
+	"github.com/zrepl/zrepl/daemon"
+	"github.com/zrepl/zrepl/util/choices"
+)
+
+type Client interface {
+	Status() (daemon.Status, error)
+	StatusRaw() ([]byte, error)
+	SignalReplication(job string) error
+	SignalSnapshot(job string) error
+	SignalReset(job string) error
+}
+
+type statusFlags struct {
+	Mode  choices.Choices
+	Job   string
+	Delay time.Duration
+}
+
+var statusv2Flags statusFlags
+
+type statusv2Mode int
+
+const (
+	StatusV2ModeInteractive statusv2Mode = 1 + iota
+	StatusV2ModeDump
+	StatusV2ModeRaw
+	StatusV2ModeLegacy
+)
+
+var Subcommand = &cli.Subcommand{
+	Use:   "status",
+	Short: "retrieve & display daemon status information",
+	SetupFlags: func(f *pflag.FlagSet) {
+		statusv2Flags.Mode.Init(
+			"interactive", StatusV2ModeInteractive,
+			"dump", StatusV2ModeDump,
+			"raw", StatusV2ModeRaw,
+			"legacy", StatusV2ModeLegacy,
+		)
+		statusv2Flags.Mode.SetTypeString("mode")
+		statusv2Flags.Mode.SetDefaultValue(StatusV2ModeInteractive)
+		f.Var(&statusv2Flags.Mode, "mode", statusv2Flags.Mode.Usage())
+		f.StringVar(&statusv2Flags.Job, "job", "", "only show specified job (works in \"dump\" and \"interactive\" mode)")
+		f.DurationVarP(&statusv2Flags.Delay, "delay", "d", 1*time.Second, "use -d 3s for 3 seconds delay (minimum delay is 1s)")
+	},
+	Run: func(ctx context.Context, subcommand *cli.Subcommand, args []string) error {
+		return runStatusV2Command(ctx, subcommand.Config(), args)
+	},
+}
+
+func runStatusV2Command(ctx context.Context, config *config.Config, args []string) error {
+
+	c, err := client.New("unix", config.Global.Control.SockPath)
+	if err != nil {
+		return errors.Wrapf(err, "connect to daemon socket at %q", config.Global.Control.SockPath)
+	}
+
+	mode := statusv2Flags.Mode.Value().(statusv2Mode)
+
+	if !isatty.IsTerminal(os.Stdout.Fd()) && mode != StatusV2ModeDump {
+		usemode, err := statusv2Flags.Mode.InputForChoice(StatusV2ModeDump)
+		if err != nil {
+			panic(err)
+		}
+		return errors.Errorf("error: stdout is not a tty, please use --mode %s", usemode)
+	}
+
+	switch mode {
+	case StatusV2ModeInteractive:
+		return interactive(c, statusv2Flags)
+	case StatusV2ModeDump:
+		return dump(c, statusv2Flags.Job)
+	case StatusV2ModeRaw:
+		return raw(c)
+	case StatusV2ModeLegacy:
+		return legacy(c, statusv2Flags)
+	default:
+		panic("unreachable")
+	}
+}